Culturable Bacterial Community Research Articles

Cultivable bacterial communities from purse-seined small pelagic fish, fishing nets and storage tanks

Cultivable bacterial communities from purse-seined small pelagic fish, fishing nets and storage tanks

The effects of Pseudomonas strains isolated from Achnatherum inebrians on plant growth: A genomic perspective.

Achnatherum inebrians is a perennial grass widely distributed in northwest China. Nearly all wild A. inebrians plants are infected by Epichloë endophytes. In this study, bacteria from the phyllosphere were isolated from leaves of both endophyte-free and endophyte-infected A. inebrians and sequenced for identification. Pseudomonas, comprising 48.12% of the culturable bacterial communities, was the most dominant bacterial genus. Thirty-four strains from 12 Pseudomonas species were used to inoculate A. inebrians seeds and plants. Results indicated that Epichloë significantly increased the diversity and richness index of the phyllosphere. Pseudomonas Sp1, Sp3, Sp5 and Sp7 had a significantly positive effect on plant growth and photosynthesis, whereas Sp10, Sp11 and Sp12 had a significantly negative effect. Whole-genome and pan-genome analysis suggested that the variability in the effects of Pseudomonas on A. inebrians was related to differences in genome composition and genomic islands.

Exploring the composition and function profiles of bacteria from wood- and soil-feeding termites for effective degradation of lignin-based aromatics

Lignocellulosic biomass (LCB) in the form of agricultural, forestry, and agro-industrial wastes is globally generated in large volumes every year. The chemical components of lignocellulosic biomass render them a substrate valuable for biofuel production. However, the rigid association of lignin, cellulose, and hemicellulose component of LCB forms a complex, hierarchical, and recalcitrant structure, which inhibits the solubilization of LCB resources for biofuel production. The learning from termites (wood-feeding and soil-feeding) and further application of their gut bacteria for lignin degradation and bioconversion remain unexplored or at its early stage. With reference to this scientific knowledge gap, this study seeks to highlight the culturable gut bacterial community in soil- and wood-feeding termites, namely Pericapritermes nitobei and Microcerotermes sp., respectively to design a future biorefinery and bioremediation technologies. In this study, a total of 40 and 67 bacterial isolates were indeed identified from Pericapritermes nitobei and Microcerotermes sp., respectively. The identified isolates from both termite species were actually classified into four different phyla: Actinobacteria, Proteobacteria, Firmicutes, and Bacteroidetes, where the phylum Actinobacteria dominated gut bacteria isolates identified from P. nitobei at 47.5 % while Proteobacteria were dominant in wood-feeding termite, Microcerotermes sp. at 46.27 %. At the genus level, the bacterial isolates enriched from the gut of Microcerotermes sp. belonged to 17 different genera, among which the bacterial genus Streptomyces (28 %) was most prevalent, followed by Enterobacter (11 %). Meanwhile, 9 genera were recorded for gut bacterial isolates from P. nitobei and were dominated by Streptomyces (37.5 %), followed by Acinetobacter (25 %). In general, the gut bacterial symbionts from both termites showed a congruency at the phyla level but were more diverged at a lower classification, inferring that different termite species evolved a unique repertoire of gut bacteria. Moreover, 61 % and 55 % of the gut bacterial isolates from the wood- and soil-feeding termites demonstrated a significant and multifunctional role in the hydrolysis of three lignocellulolytic substrates, including carboxymethyl cellulose, beechwood xylan, and aniline blue dye, indicating their unique functions and assistance to the host for the degradation of lignocellulose or other xenobiotic compounds from soil.

Epibiotic Bacteria Isolated from the Non-Indigenous Species Codium fragile ssp. fragile: Identification, Characterization, and Biotechnological Potential.

Due to their richness in organic substances and nutrients, seaweed (macroalgae) harbor a large number of epiphytic bacteria on their surfaces. These bacteria interact with their host in multiple complex ways, in particular, by producing chemical compounds. The released metabolites may have biological properties beneficial for applications in both industry and medicine. In this study, we assess the diversity of culturable bacterial community of the invasive alga Codium fragile ssp. fragile with the aim to identify key groups within this epiphytic community. Seaweed samples were collected from the Northern Tunisian coast. A total of fifty bacteria were isolated in pure culture. These bacterial strains were identified by amplification of the ribosomal intergenic transcribed spacer between the 16S and the 23S rRNA genes (ITS-PCR) and by 16S rRNA sequencing. Antimicrobial activity, biochemical, and antibiotic resistance profile characterization were determined for the isolates. Isolated strains were tested for their antimicrobial potential against human and fish bacterial pathogens and the yeast Candida albicans, using the in vitro drop method. About 37% of isolated strains possess antibacterial activity with a variable antimicrobial spectrum. Ba1 (closely related to Pseudoalteromonas spiralis), Ba12 (closely related to Enterococcus faecium), and Bw4 (closely related to Pseudoalteromonas sp.) exhibited strong antimicrobial activity against E. coli. The isolated strain Ba4, closely related to Serratia marcescens, demonstrated the most potent activity against pathogens. The susceptibility of these strains to 12 commonly used antibiotics was investigated. Majority of the isolates were resistant to oxacillin, cefoxitin, tobramycin, and nitrofurantoin. Ba7 and Ba10, closely related to the Vibrio anguillarum strains, had the highest multidrug resistance profiles. The enzymes most commonly produced by the isolated strains were amylase, lecithinase, and agarase. Moreover, nine isolates produced disintegration zones around their colonies on agar plates with agarolitic index, ranging from 0.60 to 2.38. This investigation highlighted that Codium fragile ssp. fragile possesses an important diversity of epiphytic bacteria on its surface that could be cultivated in high biomass and may be considered for biotechnological application and as sources of antimicrobial drugs.

Isolation and comparative analysis of culturable bacterial communities associated with life stages, breeding and rearing substrates of Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae) vector of bluetongue virus.

Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae) has been vectoring several arboviruses, protozoa and nematodes, leading to mortality and morbidity of livestock and wild ruminants in the tropics and subtropics. Insight into the bacterial communities associated with the vector species must be worked out. This work tries to inventorize the bacterial communities associated with this important vector species. Acquisition of gut microbiota may be the parental origin, while some are obtained through feeding during larval stages. Culicoides oxystoma possesses semi-aquatic life cycle strategies for egg-laying and larval survival. The bacteria associated with C. oxystoma were compared throughout (i) life stages: egg, larval instars, pupa, adult: male and female obtained from laboratory colony; (ii) field-collected adult: male and age-graded females; and (iii) natural breeding substrate and artificial rearing substrate. The culture-dependent bacteria were identified by Sanger sequencing of 16S rRNA, and haemolytic bacteria were screened on blood agar. Results show that Firmicutes and Proteobacteria are the predominant Phyla, of which Bacillus spp. was the most abundant across the life stages. Across the life history, Bacillus cereus, Bacillus pumilus, Bacillus tropicus, Lysinibacillus sp. and Paenibacillus sp. were retrieved routinely. Bacillus cereus and Alcaligenes faecalis were detected in the lab-reared specimens and shared between the natural breeding site and rearing medium. From the adults trapped across two locations, B. cereus, Bacillus flexus, A. faecalis, Enterococcus faecium and Pseudomonas sp. were isolated. The bacterial species associated with this vector may influence various physiological traits, such as vectorial capacity, digestion and larval development, which need further investigation.

The Impact of Environmental Gaseous Pollutants on the Cultivable Bacterial and Fungal Communities of the Aerobiome.

Understanding air microbial content, especially in highly polluted urban areas, is crucial for assessing its effect on human health and ecosystems. In this context, the impact of gaseous pollutants on the aerobiome remains inconclusive due to a lack of studies separating this factor from other contaminants or environmental factors. In this study, we aimed to experimentally assess the influence of contrasting concentrations of atmospheric gaseous pollutants as isolated variables on the composition of the aerobiome. Our study sites were contrasting Air Quality Index (AQI) sites of the Metropolitan Region of Chile, where nitric oxide (NO) was significantly lower at the low-AQI site than at the high-AQI site, while ozone (O3) was significantly higher. Cultivable aerobiome communities from the low-AQI site were exposed to their own pollutants or those from the high-AQI site and characterized using high-throughput sequencing (HTS), which allowed comparisons between the entire cultivable communities. The results showed increased alpha diversity in bacterial and fungal communities exposed to the high-AQI site compared to the low-AQI site. Beta diversity and compositional hierarchical clustering analyses revealed a clear separation based on NO and O3 concentrations. At the phylum level, four bacterial and three fungal phyla were identified, revealing an over-representation of Actinobacteriota and Basidiomycota in the samples transferred to the high-AQI site, while Proteobacteria were more abundant in the community maintained at the low-AQI site. At the functional level, bacterial imputed functions were over-represented only in samples maintained at the low-AQI site, while fungal functions were affected in both conditions. Overall, our results highlight the impact of NO and/or O3 on both taxonomic and functional compositions of the cultivable aerobiome. This study provides, for the first time, insights into the influence of contrasting pollutant gases on entire bacterial and fungal cultivable communities through a controlled environmental intervention.

Antibiotics alter development and gene expression in the model cnidarian Nematostella vectensis.

Antibiotics are commonly used for controlling microbial growth in diseased organisms. However, antibiotic treatments during early developmental stages can have negative impacts on development and physiology that could offset the positive effects of reducing or eliminating pathogens. Similarly, antibiotics can shift the microbial community due to differential effectiveness on resistant and susceptible bacteria. Though antibiotic application does not typically result in mortality of marine invertebrates, little is known about the developmental and transcriptional effects. These sublethal effects could reduce the fitness of the host organism and lead to negative changes after removal of the antibiotics. Here, we quantify the impact of antibiotic treatment on development, gene expression, and the culturable bacterial community of a model cnidarian, Nematostella vectensis. Ampicillin, streptomycin, rifampicin, and neomycin were compared individually at two concentrations, 50 and 200 µg mL-1, and in combination at 50 µg mL-1 each, to assess their impact on N. vectensis. First, we determined the impact antibiotics have on larval development. Next Amplicon 16S rDNA gene sequencing was used to compare the culturable bacteria that persist after antibiotic treatment to determine how these treatments may differentially select against the native microbiome. Lastly, we determined how acute (3-day) and chronic (8-day) antibiotic treatments impact gene expression of adult anemones. Under most exposures, the time of larval settlement extended as the concentration of antibiotics increased and had the longest delay of 3 days in the combination treatment. Culturable bacteria persisted through a majority of exposures where we identified 359 amplicon sequence variants (ASVs). The largest proportion of bacteria belonged to Gammaproteobacteria, and the most common ASVs were identified as Microbacterium and Vibrio. The acute antibiotic exposure resulted in differential expression of genes related to epigenetic mechanisms and neural processes, while constant application resulted in upregulation of chaperones and downregulation of mitochondrial genes when compared to controls. Gene Ontology analyses identified overall depletion of terms related to development and metabolism in both antibiotic treatments. Antibiotics resulted in a significant increase to settlement time of N. vectensis larvae. Culturable bacterial species after antibiotic treatments were taxonomically diverse. Additionally, the transcriptional effects of antibiotics, and after their removal result in significant differences in gene expression that may impact the physiology of the anemone, which may include removal of bacterial signaling on anemone gene expression. Our research suggests that impacts of antibiotics beyond the reduction of bacteria may be important to consider when they are applied to aquatic invertebrates including reef building corals.

Arbuscular mycorrhizal fungi and Streptomyces: brothers in arms to shape the structure and function of the hyphosphere microbiome in the early stage of interaction

BackgroundFungi and bacteria coexist in a wide variety of environments, and their interactions are now recognized as the norm in most agroecosystems. These microbial communities harbor keystone taxa, which facilitate connectivity between fungal and bacterial communities, influencing their composition and functions. The roots of most plants are associated with arbuscular mycorrhizal (AM) fungi, which develop dense networks of hyphae in the soil. The surface of these hyphae (called the hyphosphere) is the region where multiple interactions with microbial communities can occur, e.g., exchanging or responding to each other’s metabolites. However, the presence and importance of keystone taxa in the AM fungal hyphosphere remain largely unknown.ResultsHere, we used in vitro and pot cultivation systems of AM fungi to investigate whether certain keystone bacteria were able to shape the microbial communities growing in the hyphosphere and potentially improved the fitness of the AM fungal host. Based on various AM fungi, soil leachates, and synthetic microbial communities, we found that under organic phosphorus (P) conditions, AM fungi could selectively recruit bacteria that enhanced their P nutrition and competed with less P-mobilizing bacteria. Specifically, we observed a privileged interaction between the isolate Streptomyces sp. D1 and AM fungi of the genus Rhizophagus, where (1) the carbon compounds exuded by the fungus were acquired by the bacterium which could mineralize organic P and (2) the in vitro culturable bacterial community residing on the surface of hyphae was in part regulated by Streptomyces sp. D1, primarily by inhibiting the bacteria with weak P-mineralizing ability, thereby enhancing AM fungi to acquire P.ConclusionsThis work highlights the multi-functionality of the keystone bacteria Streptomyces sp. D1 in fungal-bacteria and bacterial-bacterial interactions at the hyphal surface of AM fungi.3XiVYVBxkNucerLC-WX6ofVideo

Molecular detection of Batrachochytrium dendrobatidis (Chytridiomycota) and culturable skin bacteria associated with three critically endangered species of Atelopus (Anura: Bufonidae) in Ecuador.

Chytridiomycosis is a fungal disease responsible for massive amphibian die-offs worldwide, caused by the fungus Batrachochytrium dendrobatidis (Bd). Potential symbiotic relationships between frogs and the bacteria residing on their skin-referred to as skin-bacteria-may inhibit Bd growth, aiding in resistance to this lethal disease. This research had three main objectives: (1) to detect the presence of Bd in native populations of Atelopus balios, A. bomolochos, and A. nanay in the central Andes and coastal southern regions of Ecuador; (2) to identify the culturable skin-bacteria; and (3) to analyze differences among the bacterial communities in the three Atelopus species studied. Skin swabs were collected from two populations of A. balios (107-203 m a.s.l.) and one population each of A. bomolochos and A. nanay (3,064-3,800 m a.s.l.). These swabs served two purposes: first, to detect Bd using conventional PCR; and second, to isolate culturable bacteria, which were characterized through DNA sequencing, molecular phylogeny, and community composition similarity analysis (Jaccard index). Results showed that Bd was present in all species, with positive Bd PCR amplification found in 11 of the 12 sampled amphibians. The culturable skin-bacteria were classified into 10 genera: Pseudomonas (31.4%), Stenotrophomonas (14.3%), Acinetobacter (11.4%), Serratia (11.4%), Aeromonas (5.7%), Brucella (5.7%), Klebsiella (5.7%), Microbacterium (5.7%), Rhodococcus (5.7%), and Lelliottia (2.9%). The Jaccard index revealed that bacterial genera were least similar in A. bomolochos and A. balios (J=0.10), while the highest similarity at the genus level was between A. bomolochos and A. nanay (J=0.33). At the clade-species level, only A. bomolochos and A. nanay show common bacteria (J=0.13). Culturable bacterial communities of specimens diagnosed as Bd positive (n=10) or Bd negative (n=1) share a J value of 0.1 at genus and 0.04 at species-clade level. The prevalence of Bd and the composition of cutaneous bacteria could be influenced by Bd reservoirs, Atelopus biology, and intrinsic environmental conditions. This research contributes to understanding the relationship between endangered Andean species and Bd, and explores the potential use of native skin-bacteria as biocontrol agents against Bd.

Response of Microbial Recovery Rate to Straw Return after Calcium Cyanamide Soil Disinfection

At present, returning vegetable straw in situ is an effective measure to solve environmental pollution and improve soil properties. However, the direct return of straw to the field can reduce the release rate of soil organic matter and cause serious soilborne diseases. The combined application of calcium cyanamide (CaCN2) and straw can solve this problem. The objective of this study was to determine the effect of CaCN2 combined with pepper straw return on cucumber yield, soil physicochemical properties, and soil microbial communities during 2020 to 2021 in Shandong Province, China. The treatments were designed as follows: (1) calcium cyanamide soil disinfection, CC; (2) fresh pepper straw return, LJ; (3) fresh pepper straw return combined with calcium cyanamide disinfection, LJ+CC; and (4) natural soil without straw return treatment, CK. Compared with CK, the LJ+CC treatment significantly improved cucumber production by 20%. The cultivable microbial community in the soil was temporarily inhibited during soil fumigation treatment, and the cultivable bacterial and actinomycete communities in the soil return to their initial levels after the film was removed (harvest period). The numbers of culturable bacteria and actinomycetes in the soil in the LJ+CC treatment were 4.68 × 107 CFU/g and 5.17 × 107 CFU/g, respectively, higher than those in the soil in the CC treatment. The contents of TN and OM in the LJ+CC treatment increased by 13.1% and 13.5%, respectively, compared with that in LJ. Therefore, the LJ+CC treatment enhanced soil fertility and cucumber yields. CaCN2 can promote straw decomposition and straw can promote soil microbial recovery, and their combined application is considered a feasible and sustainable technique for utilizing vegetable residues in the greenhouse. The combination of returning pepper straw to the field and calcium cyanamide technology achieves a win-win situation of resource circulation and economic circulation by converting agricultural waste into fertilizer before being put into production. Based on this, it is recommended that the straw returning technology receives strong policy support, stimulates researchers to explore the feasibility of different vegetable straw returning to the field, promotes the implementation of this technology achievement, and leverages the environmental benefits of the application of straw returning technology.

168 Characterization of the Culturable Fraction of Bovine Ocular Microbiota and Its in Vitro Antimicrobial Activities Against Pinkeye Pathogens

Abstract Pinkeye, clinically known as infectious bovine keratoconjunctivitis (IBK), is considered one of the most important ocular diseases in cattle, causing an estimated $226 million in annual losses to U.S. cow-calf producers. While Moraxella bovis is considered the principal IBK pathogen, Moraxella bovoculi has also been associated with the pathogenesis of IBK. Thus, these Moraxella species are often the target for antibiotic and/or vaccine-based treatment and prevention strategies. Despite extensive use of antibiotics, IBK infections are challenging to treat, highlighting the increased need for an antibiotic-alternative approach to control IBK. Recent evidence suggests that the microbial community associated with the bovine oculus is important for eye health, and that the ocular microbiota can be a target for enhancing disease resistance against IBK in cattle. The objectives of this study were to characterize the ocular microbiota of healthy and IBK infected cattle using sequencing and culturing techniques, and to isolate and screen commensal ocular isolates for their antimicrobial activity against M. bovis and M. bovoculi. Ocular swabs (n = 64) were collected using eSwabs from cattle diagnosed with IBK or without IBK (healthy control) before antibiotic treatment from beef herds across North Dakota. Swabs were plated onto four different agar plates (blood, Columbia blood, MRS and multi-sliced agar plates), and cultured aerobically and anaerobically. A total of 658 bacterial isolates were obtained via culturing and cryopreserved. Taxonomic identification was performed on a subset of banked isolates (n = 277) by near full-length sequencing of the 16S rRNA gene. These isolates taxonomically belong to 6 different bacterial phyla: Bacillus (42%), Firmicutes (27%), Actinomycetota (13%), Pseudomonadota (11%), Actinobacteria (5%), and Proteobacteria (2%). A total of 55 different genera were identified with Bacillus (25%), Streptococcus (13%), Staphylococcus (10%), Moraxella (6%), Macrococcus (5%), Paenibacillus (3%), Caldibacillus (3%), and Rummeliibacillus (3%) being the most dominant genera. Next, a subset of these commensal isolates (n 53) were screened for their growth inhibition against M. bovis and M. bovoculi using an agar slab method. Among the screened isolates, 6 isolates showed inhibition against M. bovis and M. bovoculi with zones of inhibition ranging from 12 mm to 28 mm. Ocular isolates identified as Weizmannia coagulans (43Y-MRSC), Lentillactobacillus buchneri (23D-MRSA) and Paenibacillus polymyxa (785-WCF) exhibited relatively strong inhibition against both Moraxella isolates. Scanning electron microscopy revealed noticeable structural and morphological damages in M. bovis and M. bovoculi cells due to Weizmannia coagulans culture-supernatant treatment. Overall, our results indicate that ocular mucosa of beef cattle is inhabited by relatively rich and diverse culturable bacterial communities, and that some ocular commensals can inhibit IBK pathogens. This suggests the potential for the development of bacterial therapeutics based on commensal ocular bacteria to mitigate IBK in cattle.

Taxonomic and functional characteristics of xerotolerant culturable bacterial community of Negev desert soil

Despite the significant expansion of the geography of soil microorganisms studies in various, including extreme natural environments, research on the biodiversity and metabolic activity of soil microbial communities under conditions of moisture deficiency are few. Biodiversity of culturable bacteria isolated from the surface horizon of the Negev desert soil (Aridic Calcisol) after pre-incubation of soil samples under the conditions of low water availability has been studied. An increase in the diversity of culturable bacteria after pre-incubation was revealed in comparison with the community isolated from the native soil. From the native and pre-incubated samples, 153 phenotypically unique pure cultures of bacteria from 22 genera belonging to the phyla Actinomycetota, Pseudomonadota, Bacillota, and Bacteroidota were isolated and identified. The taxonomic diversity of culturable bacteria isolated from the sample pre-incubated at a water activity (Aw) of 0.90 was two times higher than that obtained from the native soil. The strain of the genus Pedobacter has been identified, which may be a representative of a previously undescribed bacterial species. Bacteria of the genera Aerococcus, Bacillus, Brevibacterium, Staphylococcus, and Stenotrophomonas capable of growing at Aw 0.91 were found. One strain of the genus Microlunatus has been identified that is capable of growing on a nitrogen-free medium, exhibiting amylase and protease activity, and capable to growth on a medium with Aw down to 0.96. The obtained results confirm the hypothesis that arid ecosystems, in particular, desert soils and sediments, are a depository of a previously unexplored taxonomic diversity of bacteria with unique physiological properties that are promising for study and potential implementation in biotechnological processes.

Assessing the functional diversity of rhizobacteria from cacao by partitioning root and shoot biomasses.

Plant-microbe interactions are critical for the sustainability of agricultural production. In this study, our aims were to characterize the genetic and functional diversity of the culturable bacterial community associated with the cacao rhizosphere and access their potential for growth promotion of cacao seedling. Culture-dependent and molecular methods were used to characterize the population densities and diversity of bacterial communities from soil and cacao plants at two locations and two plant ages. A total of 63 strains were identified through hsp60 sequencing. Pseudomonas and Enterobacter were the most abundant genera in association with the cacao rhizosphere, whereas Bacillus was more numerous in soil. Parameters of seedling growth promotion were evaluated 60days after inoculation of seeds, with partition of the assessments into root and shoot weight. Each isolate showed beneficial, neutral or deleterious effects on plant growth, depending on the isolate and on the parts of plant assessed. Interestingly, although an apparent overall decrease in total biomass of seedlings (roots + shoots dry matters) was observed for the majority of isolates (89%), 94% of all isolates, in fact, revealed an increase in plant roots/shoots dry biomass ratio. Despite that part of the isolates (35%) appeared to significantly decrease plant height, and that 65% did not influence plant height (neutral effect), 18 had significantly increased root dry biomass; nevertheless, seven of these root growth-increasing isolates simultaneously decreased shoots-related growth parameters. The results of this study evidentiated the functional diversity of culturable cacao rhizobacteria and how the partitioning of roots and shoots in the assessment of plant growth parameters could reveal the biotechnological potential of these isolates for promoting growth of clones for rehabilitation of commercial cacao plantations. KEY POINTS: • The most common culturable bacteria in cacao roots were Pseudomonas and Enterobacter • Most culturable bacteria from cacao roots increased the root/shoot ratio • Roots and shoots should be examined separately to detect cacao beneficial bacteria.

Convivina is a specialised core gut symbiont of the invasive hornet Vespa velutina.

We provide a culturomics analysis of the cultivable bacterial communities of the crop, midgut and hindgut compartments, as well as the ovaries, of the invasive insect Vespa velutina, along with a cultivation-independent analysis of samples of the same nest through 16S rRNA amplicon sequencing. The Vespa velutina bacterial symbiont community was dominated by the genera Convivina, Fructobacillus, Lactiplantibacillus, Lactococcus, Sphingomonas and Spiroplasma. Lactococcus lactis and Lactiplantibacillus plantarum represented generalist core lactic acid bacteria (LAB) symbionts, while Convivina species and Fructobacillus fructosus represented highly specialised core LAB symbionts with strongly reduced genome sizes. Sphingomonas and Spiroplasma were the only non-LAB core symbionts but were not isolated. Convivina bacteria were particularly enriched in the hornet crop and included Convivina intestini, a species adapted towards amino acid metabolism, and Convivina praedatoris sp. nov. which was adapted towards carbohydrate metabolism.

In vitro biochemical characterization and identification of hemolytic bacteria associated with life history of Culicoides peregrinus (Diptera: Ceratopogonidae), a vector of bluetongue virus.

Gut bacterial communities in insects provide several beneficial roles like nutrition, digestion, fecundity, and survival of the host. The microbial communities of Culicoides spp. (Diptera: Ceratopogonidae) vary with parity, developmental stages, and environmental factors. Previous studies have revealed the presence of hemolytic bacteria in adult Culicoides peregrinus Kieffer (Diptera: Ceratopogonidae), an important vector of bluetongue virus (BTV). Our objectives were (i) to identify bacterial communities with hemolytic activities associated with all life stages and (ii) to compare between reared and field-collected adults including age graded females. Bacterial identification followed Sanger sequencing of 16S rRNA. In vitro biochemical characterizations including antibiotic sensitivity tests were also done. The majority of bacterial species were beta hemolytic with one, Alcaligenes faecalis, showing alpha hemolysis. Most bacterial species were observed in field-collected adults except Proteus spp. Throughout the life history of the vector, Bacillus cereus (CU6A, CU1E) and Paenibacillus sp. (CU9G) were detected indicating their possible role in blood digestion within the gut of this vector species. In vivo hemolytic activities of these culturable bacterial communities within this vector may be addressed in future. These hemolytic bacterial communities may be targeted to develop novel and effective strategies for vector control.

16S rRNA gene‐based identification and plant growth‐promoting potential of cultivable endophytic bacteria

AbstractEndophytic bacteria play essential roles in plant growth and fitness through nitrogen fixation, nutrient solubilization, and phytohormone production. However, the plant growth‐promoting (PGP) potential of endophytic microorganisms inhabiting vegetables is underexplored. Thus, this study investigated the endophytic bacteria of vegetable crops for their PGP properties using the culture‐dependent technique. Recovered isolates were identified by sequencing the partial 16S rRNA gene using Sanger sequencing. The isolated endophytic bacteria belonged to 15 genera and 39 different species. Bacillus, Enterobacter, Pantoea, and Pseudomonas were the predominant genera and had high phosphate solubilization and siderophore production potential. The isolates differentially produced indole‐3‐acetic acid and ammonium in the range 0.14–44.48 μg mL–1 and 0.77–93.24 mg L–1, respectively. Pseudomonas azotoformans, Stenotrophomonas maltophilia, and Serratia liquefaciens showed a high level of siderophore production, which was not significantly (p > 0.05) different across the plant and organ types. More than 21% of endophytes could produce gelatinase, protease, amylase, and cellulase, contributing to their diverse ecosystem functions. Bacterial density and species composition varied across the vegetable species, organs, and farm locations but were higher in the stems compared with other organs. However, the vegetable organ had no significant (p > 0.05) influence on the bacterial population density, except for the interaction of plant species and organs. Overall, this study provides basic knowledge about the cultivable endophytic bacterial community of vegetables and reveals diverse endophytic bacteria useful in bioinoculant formulations for improving crop productivity.

Microbiological quality and cultivable bacterial community of fresh and ripened Minas cheeses made from raw and pasteurised milk

The microbiological and physicochemical characteristics of 56 samples of Brazilian fresh (Minas frescal cheese, MFC) and ripened (Minas padrão cheese, MPC; Minas artisanal cheese, MAC) cheeses produced from pasteurised (MFC and MPC) or raw milk (MAC) were evaluated. Significant differences were observed between samples, with a positive emphasis on microbiological quality for MPC. MALDI-TOF MS identified a diverse bacterial community from the 808 colonies isolated from different culture media. Staphylococcus aureus (34.32%) and Escherichia coli (35.59%) were the most isolated species. The eae gene, which confers virulence on E. coli strains, was observed in 23 samples (41.07%), and in 21.05%, 27.78%, and 73.68% of MFC, MPC and MAC samples, respectively. There was no correlation between the evaluated indicators and the presence of eae-positive cheese samples. The choice of the ideal microbiological indicator must be specific, considering the physicochemical characteristics and the raw milk of the different types of cheese.

Vertical profile of culturable bacteria from the Makassar Strait, Indonesia

Abstract. Siallagan ZL, Kristianti T, Dwivany FM, Nugrahapraja H, Fretes CED, Fadli M, Trinugroho JP, Radjasa OK, Susanto RD. 2023. Vertical profile of culturable bacteria from the Makassar Strait, Indonesia. Biodiversitas 24: 1356-1365. Indonesia's extensive maritime background is a rich biological and chemical diversity source. This diversity has become as source of unique chemical compounds with the potential for industrial development as enzymes, molecular probes, chemicals, pharmaceuticals, cosmetics, nutritional supplements, and agrochemicals. The present study aimed to analyze the community composition of culturable bacteria from three different layers of depth from Makassar Strait using high throughput DNA Illumina sequencing of 16S rRNA. Bioinformatic analysis has rendered 140336 high-quality sequences with an average of 124127 sequences per sample and a mean read length of 428 bp. Results showed that Firmicutes and Proteobacteria were the two most abundant phyla. Taxonomic analysis showed that Firmicutes dominated all samples. Genus Streptomycetes and Psychrobacter occurred mainly in the culture from the surface layer. Species richness and diversity for the bacterial communities at 100 m were higher than those at 5 m and 200 m. PCA plot, NMDS plot, and UPGMA clustering demonstrated that the culturable bacterial community compositions of 100 and 200 ms were highly similar and distinct from those in 5 m. This research discovered microbes with potential as sources of marine natural products, including Streptomyces, Paenibacillus, Bacillus, Psychrobacter, Arthrobacter, Bradyrhizobium, Gemmatimonas, and Acidobacteria.

Further Bacteriological Analysis of Annual Pheasantshell (Actinonaias Pectorosa) Mussel Mortality Events in the Clinch River (Virginia/Tennessee), USA, Reveals a Consistent Association with Yokenella Regensburgei

Pheasantshell (Actinonaias pectorosa) mussels in the Clinch River (Tennessee/Virginia, USA) have declined dramatically in recent years. The bacterium Yokenella regensburgei was first isolated with high prevalence from Pheasantshells during the peak of a 2017 mortality event, but it was not identified after mortality subsided a few months later. Since 2017, Pheasantshell mortality in the Clinch River has occurred each autumn. We extended the investigation of culturable bacterial communities in the Clinch River during mussel mortality events in 2018, 2019, and 2020 and examined the spatial and temporal distribution of bacterial genera among Pheasantshells, as well as among other unionid mussels. We identified Y. regensburgei each year, almost exclusively during active mortality events. The significance of Y. regensburgei remains unclear, but the continued association of this bacterium with mussel mortality events warrants further study.

Composition of the culturable bacterial community associated with the water column and soft tissues from oysters of the mangrove ecosystem at Honda Swamp, Colombian Caribbean

The study of bacterial communities is highly relevant in relation to the knowledge of global biological biodiversity and the biogeochemical cycles of the planet. Microbiological activity is the basis of ecosystems functioning, among these are the mangroves, which offer a wide variety of goods and services to humanity. Nevertheless, they have been severely impacted by anthropogenic activities such as felling, heavy metal pollution, water enrichment, overexploitation of resources, among others. This research aimed to characterize the culturable bacterial community from the water column and the oyster Crassostrea rhizophorae muscle tissue in a mangrove ecosystem from the Cartagena Bay, Colombian Caribbean as a baseline for future studies on bioremediation treatments. To accomplish this, four samplings were conducted over the course of a year, including contrasting climatic seasons (e.g., windy and rainy), collecting oyster individuals from mangroves and samples from superficial water. The bacterial community comprised 25 species, from which 9 were exclusive for the oyster tissue, 7 for the water column, and 9 generalists isolated from both types of samples. Enterobacter cloacae was the most frequent species during the year, followed by Escherichia coli and Erwinia sp.There were significant differences in the species composition between the sampling months (ANOSIM, R = 0:492; p=D 0:001), because of the presence of a higher number of exclusive species in December than in the other months. Furthermore, the physicochemical variables that presented a major influence on the bacterial community composition were the wind velocity and the dissolved oxygen. The review of this research findings will allow to detect if any of the identified species could be exploited for bioremediation treatments, and it will contribute to the preservation of marine-coastal water bodies biodiversity.