Pure Cultures Of Bacteria Research Articles

Biological Nitrification Inhibitors with Antagonistic and Synergistic Effects on Growth of Ammonia Oxidisers and Soil Nitrification

Biological nitrification inhibition (BNI) refers to the plant-mediated process in which nitrification is inhibited through rhizospheric release of diverse metabolites. While it has been assumed that interactive effects of these metabolites shape rhizosphere processes, including BNI, there is scant evidence supporting this claim. Hence, it was a primary objective to assess the interactive effects of selected metabolites, including caffeic acid (CA), vanillic acid (VA), vanillin (VAN), syringic acid (SA), and phenylalanine (PHE), applied as single and combined compounds, against pure cultures of various ammonia-oxidising bacteria (AOB, Nitrosomonas europaea, Nitrosospira multiformis, Nitrosospira tenuis, Nitrosospira briensis) and archaea (AOA, Nitrososphaera viennensis), as well as soil nitrification. Additionally, benzoic acid (BA) was examined as a novel biological nitrification inhibitor. All metabolites, except SA, tested as single compounds, achieved varied levels of inhibition of microbial growth, with CA exhibiting the highest inhibitory potential. Similarly, all metabolites applied as single compounds, except PHE, inhibited soil nitrification by up to 62%, with BA being the most potent. Inhibition of tested nitrifying microbes was also observed when compounds were assessed in combination. The combinations VA + PH, VA + CA, and VA + VAN exhibited synergism against N. tenuis and N. briensis, while others showed antagonism against N. europaea, N. multiformis, and N. viennensis. Although all combinations suppressed soil nitrification, their interactions against soil nitrification revealed antagonism. Our findings indicate that both antagonism and synergism are possible in rhizospheric interactions involving BNI metabolites, resulting in growth inhibition of nitrifiers and suppression of soil nitrification.

Study of biotechnological potential of hydrocarbon-oxidizing bacteria from oil-contaminated soils of the Uzen oil field

Background: Oil-contaminated soils are one of the significant environmental concerns in Western Kazakhstan. Cleaning soils from oil contamination is becoming extremely important. Biological soil treatment, which uses hydrocarbon-oxiding bacteria for microbiological remediation, is a more environmentally friendly and delicate method of soil treatment than any other currently used technology (physical, chemical, biological). One of the important aspects of microbiological remediation is the use of bacteria endomimic to the treated soil. This guarantees the most effective soil purification, as the bacteria perform in relatively optimal conditions for themselves. The soil of the Mangistau region, especially the coastal regions, is distinctive due to its high mineralisation and low moisture content, which have helped to form a specific microflora that is adapted to these conditions. Aim: The study aims to search and isolate highly effective hydrocarbon-oxidizing bacteria that are native to highly mineralized soils of the Uzen oil field. Materials and methods: The research employs a variety of analytical techniques, including water chemistry analysis and infrared spectrometry, as well as the microbiological culture of aerobic bacteria on liquid and dense media in environments (temperature and salinity) that closely resemble their native ecotopes. Results: Four enrichment cultures of hydrocarbon-oxidizing bacteria were obtained, and three pure cultures of oil-oxidizing bacteria were isolated. Their hydrocarbon-oxidizing efficiency has been studied. On the basis of heavy, extremely viscous paraffinic oil from the Uzen field, their hydrocarbon-oxidizing efficiency was examined. Conclusion: In this study, active enrichment cultures of halophilic hydrocarbon-oxidizing bacteria as well as active accumulative cultures of halophilic and moderately thermophilic aerobic bacteria were obtained. These bacteria are capable of oxidising a wide range of hydrocarbons, including high-molecular polycyclic and sulfur-containing compounds. Their high biotechnological potential will be studied in further studies.

ШҰБАТ ҚҰРАМЫНДАҒЫ СҮТҚЫШҚЫЛДЫ БАКТЕРИЯЛАР МЕН АШЫТҚЫЛАРДЫ ИДЕНТИФИКАЦИЯЛАУ

The importance of fermented dairy products for human nutrition cannot be overestimated. Despite the existence of many scientific studies on fermentation processes in the production of dairy products from cow's milk, the number of works dealing with national fermented dairy products based on camel's milk is limited. Worldwide, most of these beverages are mixed fermentation products. The study of lactic acid and alcoholic fermentation has gained a fairly wide scientific popularity, but the peculiarities of this process depend largely on the species-specific characteristics of pure cultures of lactic acid bacteria and yeasts acting as its main causative agents. Despite the diversity of available cultures, there is a growing interest in identifying and studying new species of lactic acid bacteria and yeasts. To determine the species composition of lactic acid bacteria and yeasts characteristic of the native microflora of Shubat, a study was conducted to isolate pure cultures and identify them. The microflora of Shubat, produced by the method of spontaneous fermentation, mainly includes Lactobacillus plantarum, Lactococcus lactis, Streptococcus thermophilus, and the yeasts Brettanomyces anomalus, Naumovozyma castellii, Candida kefyr and Kazachstania unispora, which have marked antagonistic properties towards Escherichia coli. Further research in this area will help not only to understand the mechanism of interaction between different microorganisms.

Degradation of pretilachlor and fenclorim and effects of these compounds on bacterial communities under anaerobic condition.

Pretilachlor and safener fenclorim are the main components of herbicides widely applied to control weeds. Although some pure cultures of bacteria and fungi which degraded these compounds under aerobic conditions were isolated, no isolated pretilachlor- and fenclorim-degrading bacterial strains under anaerobic condition had been available. In this study, the degradation of these compounds and the effects of them on bacterial community structures were investigated under anaerobic conditions. The dissipation rates of pretilachlor and fenclorim in slurries were in the order: soil from paddy field ≈ sediment from river > sediment from mangrove. Moreover, three pretilachlor-degrading bacterial strains (Pseudomonas sp. Pr1, Proteiniclasticum sp. Pr2 and Paracoccus denitrificans Pr3) and two fenclorim-degrading strains (Dechloromonas sp. Fe1 and Ralstonia pickettii Fe2) isolated from a slurry of paddy soil utilized the substrates as sole carbon and energy sources under anaerobic conditions. The degradation of pure pretilachlor and fenclorim at various concentrations by corresponding mixed pure cultures followed the Michaelis-Menten model, with the maximum degradation was 3.10 ± 0.31µM/day for pretilachlor, and 2.08 ± 0.18µM/day for fenclorim. During the degradation, 2-chloro-N-(2,6-diethylphenyl) acetamide and 2,6-dimethylaniline were produced in pretilachlor degradation, and benzene was a product of fenclorim degradation. The synergistic degradation of both substrates by all isolated bacteria reduced the metabolites concentrations accumulated in media. This study provides valuable information on effects of pretilachlor and fenclorim on bacterial communities in soil and sediments, and degradation of these substrates by isolated bacteria under anaerobic condition.

Characteristics of fermentation changes in the dough for rye-wheat bread with the addition of propionic and lactic acid bacteria

The quality of bread directly depends on several physical and chemical indicators of the quality of flour, which is used in the technology of making products. Various types of flour, phyto-additives, oils, and leavening microorganisms are added to its recipe to improve the quality and increase the biological value of bread. Pure cultures of lactic acid and propionic acid bacteria are among the fermenting microbiota most often used in the technological process of bread production. The work aimed to determine the effect of adding pure cultures of lactic acid and propionic acid bacteria on the technological process of bread production. Three samples of dough and dough were prepared: the first with lactic acid bacteria and yeast; the second – propionic and lactic acid bacteria and yeast; the third only on a yeast base. Then, samples of rye-wheat dough were mixed in these ovens, and bread was baked. The symbiotic effect of propionic acid bacteria on the acidification of the environment, that is, on the development of yeast and lactic acid bacteria, was established because it was sample № 2 in which this entire microbial landscape was present that had the highest acidity of the dough. An interdependent relationship between added bacteria to the wort and reduction in fermentation time was revealed. In test № 2, the time required to reach the final fermentation process was about 77 min, about 30 min faster than in the control test. In dough № 2 with added microbiota, the lifting force time was the lowest. Therefore, the addition of propionic and lactic acid bacteria to the dough at the same time as yeast contributes to the active gas-forming ability of the dough. Thus, introducing this microbiota into the steam will increase semi-finished products in a short production time.

Evaluation of UVLED disinfection for biofouling control during distribution of wastewater effluent

Abstract A commercially available UVLED flow-through device, operating at 40 mJ/cm2, was examined for biofilm control on irrigation pipe material fed by wastewater effluent. Biofouling was monitored through total coliform counts, crystal violet (CV) staining, and ATP analyses. A UV fluence of 40 mJ/cm2 at 280 nm retarded biofilm formation; however, complete biofilm prevention by UV treatment was not achieved despite a high inactivation of planktonic cells. After 5 days of the study, the total coliform and CV biofilm quantification assays between the UV-treated and control bioreactor coupons were not statistically different. The total coliform counts indicated a stable biofilm cell concentration was reached; the CV assay showed biofilm biomass accumulation with time. The ATP results revealed higher coupon ATP on the UV-treated coupons than the control coupons by day 5. The results provoke an interesting discussion surrounding the contribution of viable cells, represented by total coliforms, and extracellular polymeric substance (EPS) to total biofilm biomass. This study also highlighted a need for further investigation into the relationship between ATP responses and complex UV-stress responses of diverse microbial communities as opposed to pure bacteria cultures.

New Enriched Culture Media for Culturing Streptococcus pyogenes by using Spirulina Powder

Background and Aim: Fastidious bacteria require special nutrients and growth factors to grow on enriched culture media. Many enriched culture media were developed for culturing and isolating fastidious bacteria in pure cultures. The present study investigates the ability of spirulina powder to support the fastidious bacteria growth in pure culture compared to ordinary enriched media, e.g., Blood agar and Chocolate agar.
 Methods: Spirulina powder was used as a nutrient source with some additives to prepare different types of Spirulina media. Reference strain ATCC (19615) and three clinical isolates of Streptococcus pyogenes were examined for their growth on the developed candidate medium. Three formulations of spirulina powder were used: Medium 1, Medium 2, and Medium 3.
 Results: All spirulina media supported the growth of streptococcus pyogenes and there was no significant difference in the morphology and cultural characteristics on the blood agar and chocolate agar media. Colonies size of streptococcus pyogenes were slightly smaller size on spirulina media.
 Conclusion: Spirulina media is a possible candidate that can be used as enriched culture media for culturing and isolating fastidious bacteria such as Streptococcus pyogenes.
 Keyword: Spirulina powder, enriched culture media, Streptococcus pyogenes.

Infectious sporadic bovine abortions: retrospective analysis.

Infectious sporadic abortions in cattle are mainly caused by opportunistic bacteria and fungi usually present in environmental or gastrointestinal and reproductive microbiota of healthy animals. A retrospective analysis was carried out to evaluate the main opportunistic microorganisms involved in bovine abortions recorded at INTA Balcarce (Argentina) from 1997 to 2023, accounting for 2.2% of the total diagnosed etiologies of bovine abortion. The opportunistic agents identified as the cause of abortion in 29 fetuses were bacteria (90%) and fungi (10%). Escherichia coli (n = 8), Trueperella pyogenes (n = 5), and Histophilus somni (n = 4) were the bacterial species most often identified as causing infectious abortions, whereas Aspergillus spp. (n = 3) was implicated in all fungal abortions identified. Pure culture of bacteria or fungus was achieved from abomasal content and/or lung essential. Main microscopic findings were bronchopneumonia, myo- and epicarditis, meningitis, and portal hepatitis. Herein, we highlight the importance of detecting potential infectious bacteria in cultures to improve etiological diagnosis of bovine abortions associated with compatible microscopic findings to confirm the etiology.

The regulation effect of preventing soil nitrogen loss using microbial quorum sensing inhibitors

Preventing soil nitrogen (N) losses driven by microbial nitrification and denitrification contributes to improving global environmental concerns caused by NO3−-N leaching and N2O emission. Quorum sensing (QS) signals regulate nitrification and denitrification of N-cycling bacteria in pure culture and water treatment systems, and mediate the composition of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in activated sludge. However, whether disrupting QS could prevent soil N losses remains unclear. This study explored the feasibility of applying quorum sensing inhibitors (QSIs) as an innovative strategy to reduce N losses from agricultural soils. The two QSIs, penicillic acid and 4-iodo-N-[(3S)-tetrahydro-2-oxo-3-furanyl]-benzeneacetamide (4-iodo PHL), were more effective in reducing N losses than traditional inhibitors, including N-(n-butyl) thiophosphoric triamide and 3,4-dimethylpyrazole phosphate. After 36 days of aerobic incubation, penicillic acid and 4-iodo PHL inhibited nitrification by 39% and 68%, respectively. The inhibitory effects are attributed to the fact that 4-iodo PHL decreased the abundance of archaeal and bacterial amoA genes, as well as the relative abundance of Candidatus Nitrocosmicus (AOA), Candidatus Nitrososphaera (AOA), and Nitrospira (nitrite-oxidizing bacteria/comammox), while penicillic acid reduced archaeal amoA abundance and the relative abundance of Nitrosospira (AOB) and the microbes listed above. Penicillic acid also strongly inhibited denitrification (33%) and N2O emissions (61%) at the peak of N2O production (day 4 of anaerobic incubation) via decreasing nitrate reductase gene (narG) abundance and increasing N2O reductase gene (nosZ) abundance, respectively. Furthermore, the environmental risks of QSIs to microbial community structure and network stability, CO2 emissions, and soil animals were acceptable. Overall, QSIs have application potential in agriculture to reduce soil N losses and the associated effect on climate change. This study established a new method to mitigate N losses from the perspective of QS, and can serve as important basis of decreasing the environmental risks of agricultural non-point source pollution.

NEW ENRICHED CULTURE MEDIA FOR CULTURING HAEMOPHILUS INFLEUNZAE

Background and aim: Fastidious bacteria require special nutrients and growth factors to grow on enriched culture media. Many enriched culture media were developed for culturing and isolating fastidious bacteria in pure cultures. A number of defined media have been described, but their use often leads to frustration. The present study investigates the ability of spirulina powder to support the fastidious bacteria growth in pure culture compared to ordinary enriched media, e.g Blood agar and Chocolate agar. Methods: Spirulina powder was used as a nutrient source with some additives to prepare different types of Spirulina media. Reference strain of Haemophilus infleunzae (H.imfleunzae) ATCC (49347) and three clinical isolates were examined for their growth on the developed candidate medium. Three formulations of spirulina powder were used: Medium 1, Medium 2, and Medium 3. Results: spirulina media type 2 and 3 supported the growth of H infleunzae and there was no significant difference in the morphology and cultural characteristics on chocolate agar media. Colonies size of H infleunza were slightly smaller size and white in color on spirulina media. Conclusions: Spirulina media type 2 and 3 are a possible candidate that can be used as enriched culture media for culturing and isolating fastidious bacteria such as H.infleunzae.

Failure of a proprietary fluorescent in situ hybridization assay to detect M. avium subspecies paratuberculosis in archived frozen brain from patients with Multiple Sclerosis

Objectives: Multiple Sclerosis is a chronic, enigmatic, progressive central nervous system “inflammatory” disease, with no know etiology. As with other “inflammatory” diseases there is the possibility that a cryptic infectious trigger may play a role in initiating Multiple Sclerosis. M. avium subspecies paratuberculosis causes Johne’s disease in ruminants and may be an infectious trigger in Crohn’s disease. In this study, frozen archived brains from patients with Multiple Sclerosis, pure culture of multiple bacteria and circulating WBCs were assayed with proprietary (AffymetrixÔ RNA view®) Tissue and Cell fluorescent in situ hybridization assay for MAP RNA. Results: Repetitively, false positive signal was observed in the “No-Probe” negative control. Despite advice from the technical staff at Affymetrix, multiple experimental modifications could not prevent positive signal in the “No-Probe” negative control. When studying human white blood cells under specific storage conditions, we observe positive signal with human house-keeping genes, when no signal is seen in the No-Probe controls. Conclusions: We conclude, that when performed according to manufactures instructions and with multiple variations on the manufactures recommended suggestions to correct for false positive signal, that the AffymetrixÔ RNA view® TISSUE assay cannot be used to detect M. avium subspecies paratuberculosis in pre-frozen brains of humans with Multiple Sclerosis. In contrast, using the AffymetrixÔ RNA view Cell fluorescent in situ hybridization system, evaluating human white blood cells, we reliably identify human house-keeping genes. This indicates that the Cell fluorescent in situ hybridization assay may be useful when evaluating circulating cells for specific pathogens.

Prevalence of Pangasius Fish Disease in Nepal

Objectives: This study was conducted to identify bacterial pathogens in both symptomatic and asymptomatic enteric septicemic infection of Pangasiaus hypophthalmus and evaluate their susceptibility to antibiotics. Methods: The totals of 120 kidney and liver swab samples of fish were collected from different places of Nepal. The samples were processed to identify the causative agent using pure culture of bacteria through streak plate techniques and different biochemical tests. To assess the susceptibility of the isolated bacteria to antibiotics Ciprofloxacin, Tetracycline, Doxycycline, Gentamycin, Ampicillin/ sulbactam, and Tobramycin were used. Results: The estimated prevalence of pathogenic bacteria is 27 per 10000 populations. Three pathogenic bacteria i.e. Edwardsiella ictaluri 57.7% (56/97), Aeromonas hydrophila 24.7% (24/97), and Pseudomonas fluorescence 17.5% (17/97) were identified in the studied asymptomatic and symptomatic Pangas fish disease. E. ictaluri was major isolates which was causative agent for the disease, enteric septicemia of catfish. Among the total bacterial isolates 100% bacterial isolates were sensitive to Ciprofloxacin and 84% to Gentamycin. Whereas 100% were resistance to Ampicillin and 84% to Tetracycline. And Tobramycin (60.8%) and Doxycycline (64.9%) showed intermediate result. Conclusion: Ciprofloxacin and Gentamycin could be administered to control enteric septicemia of catfish in Pangas. This study provides information to strategies to reduce economic losses to farmer and reduce possible health hazards.

THE INFLUENCE OF NUTRIENTS AND LACTULOSE PREBIOTIC ON THE FERMENTATION PROCESSES IN THE TECHNOLOGY OF RECEIVING A FUNCTIONAL FOOD PRODUCT WITH AN INCREASED TITER OF VIABLE LACTIC ACID BACTERIA

A study of the influence of biologically active substances (fat-soluble vitamins, omega-3 fatty acids and vitamin D, as well as water-soluble vitamin C), prebiotic lactulose on the titer of viable cells of lactic acid bacteria was carried out for the further use of the obtained research results in the biotechnology of functional food products, obtained thanks to the successful course fermentation processes. Experiments have proven the expediency of using biologically active substances as stimulators of the growth of lactic acid bacteria, which contribute to the increase of biomass and support of their vital activity for 192 hours. Research has established that at the end of the experiment (192 hours), the highest titer of lactic acid bacteria was recorded in samples 1, 2, 3, 4, to which the prebiotic lactulose was added in the amount of 1, 3, 5 and 7 %, respectively. This is due to the fact that the prebiotic acts as a specific substrate that is used by the symbiosis of pure cultures of lactic acid bacteria for a long time, unlike milk sugar. Analyzing the obtained data, it is indicated that thanks to the addition of fat-soluble nutrients omega-3 fatty acids and vitamin D, as well as water-soluble vitamin C, there is a significant increase in the titer of viable cells of probiotic cultures at 6 and 24 hours of the experiment, although at the end of the experiment (by 192 hour) in these samples, an insignificant decrease of this indicator was recorded — from 10 to 8.9 log cells/ml. In the control sample (without the addition of biologically active substances and lactulose prebiotic), a significant decrease in the titer of viable cells of lactic acid bacteria was noted, compared to the test samples to which nutrients were added. The titer of lactic acid bacteria cells in the control sample was reduced by 192 hours from 8.5 to 5.5 log cells/ml. It is recommended to use the studied nutrients in the indicated concentrations to stimulate the growth and maintain the viability of lactic acid bacteria cultures in the technology of production of functional food products.

Evaluation of the Novel mTA10 Selective Broth, MSB, for the Co-Enrichment and Detection of Salmonella spp., Escherichia coli O157 and Listeria monocytogenes in Ready-to-Eat Salad Samples.

Multiplex assays implementing DNA-based methods have been demonstrated as suitable alternatives to culture-based microbiological methods; however, in most cases, they still require a suitable enrichment step. Finding suitable enrichment conditions for different bacteria may result in challenges. In the present study, a novel selective broth named MSB (mTA10 selective broth) was formulated for the simultaneous recovery of Salmonella spp., E. coli O157:H7 and L. monocytogenes. Attention was paid to ensure the optimal enrichment of L. monocytogenes as its enrichment is more challenging. To this end, cellobiose was added to increase the growth of L. monocytogenes, and sodium pyruvate was also added to improve the recovery of stressed bacteria. Four selective agents were added, namely nalidixic acid, sodium cholate, lithium chloride and potassium tellurite, to control the growth of interfering microorganisms. It was concluded that the novel broth was suitable for the simultaneous enrichment of the target pathogens, allowing them to reach concentrations higher than 7 log CFU/mL for each bacterium in pure culture. Furthermore, all heavily contaminated ready-to-eat salad samples reached concentrations higher than 5 log CFU/g. Finally, after 24 h of enrichment of spiked salad, it was possible to detect concentrations below 10 CFU/25 g.

Rapid detection of Salmonella typhimurium by photonic PCR-LFIS dual mode visualization

Salmonella spp., as one of the foodborne pathogens, is a severe threat to global public health. Rapid screening of salmonella spp. in contaminated food with low infective doses is the key to preventing food poisoning. In this study, a fast visualization method for detecting Salmonella typhimurium (S. typhimurium) was developed based on photonic PCR and AuNPs lateral-flow immunochromatography strip (LFIS). In addition, quantitative detection of target bacteria could be achieved by utilizing the photothermal effect of AuNPs, and the sensitivity could be improved by amplifying the photothermal signal. On the optimized conditions, the developed photonic PCR-LFIS assay was highly sensitive, with a detection limit as low as 19 cfu mL−1 of bacteria in pure culture after laser irradiation, and highly specific, exhibiting no cross-reaction with Salmonella enteritidis, Listeria monocytogenes, Escherichia coli, and Staphylococcus aureus. Notably, S. typhimurium could be detected in pork, egg white, and milk without pre-treatment, with the recovery rates of the three samples between 81 % and 109 %. In conclusion, the photonic PCR-LFIS assay realizes sensitive, simple, and rapid detection of S. typhimurium.

Influence of photodynamic action on pure and mixed cultures of gram-negative bacteria: related to growth mechanisms

Gram-negative bacteria present a significant challenge to conventional treatments due to their structurally complex cell walls, setting them apart from their gram-positive counterparts. These structural distinctions, coupled with various antimicrobial resistance mechanisms, make them highly resilient. Photodynamic inactivation (PDI) has emerged as a promising technique to address this challenge, capitalizing on oxidative stress induced by the synergy of light and a photosensitizer (PS). In this study, we delved into the application of PDI and its repercussions on both Klebsiella pneumoniae and Escherichia coli bacteria, in both pure cultures and mixed populations. Our investigation encompassed an analysis of changes in growth curves when influenced by photodynamic and the response to the susceptibility to gentamicin. Methods: Various concentrations (50 μM, 100 μM, and 150 μM) of synthetic curcumin solutions served as PS in treatment groups. Additionally, solvents such as dimethyl sulfoxide and 0.1% sodium dodecyl sulfate (SDS) were evaluated to enhance PS mobility and absorption. Growth curves for pure and mixed cultures were established, both pre- and post-PDI, and in the presence of 0.1% SDS. Blue light irradiation at 30 J cm−2 and 450 nm was employed. The minimum inhibitory concentration (MIC) of the antibiotic was determined with and without PDI + SDS. Results: While PDI did not achieve optimal bacterial reduction for these strains, it did introduce oxidative damage that has the potential to affect other critical aspects of the temporal progression of cultures and their responses to antibiotics. Conclusion: This study shows that even with the minimal impact of PDI in the presence of 0.1% SDS, observable alterations in bacterial growth profiles and MIC values occur and can be used in favor of treatment involving such infections.

Diversity and ice nucleation activity of Pseudomonas syringae in drone-based water samples from eight lakes in Austria.

Bacteria from the Pseudomonas syringae complex (comprised of at least 15 recognized species and more than 60 different pathovars of P. syringae sensu stricto) have been cultured from clouds, rain, snow, streams, rivers, and lakes. Some strains of P. syringae express an ice nucleation protein (hereafter referred to as ice+) that catalyzes the heterogeneous freezing of water. Though P. syringae has been sampled intensively from freshwater sources in the U.S. and France, little is known about the genetic diversity and ice nucleation activity of P. syringae in other parts of the world. We investigated the haplotype diversity and ice nucleation activity at -8 °C (ice+) of strains of P. syringae from water samples collected with drones in eight freshwater lakes in Austria. A phylogenetic analysis of citrate synthase (cts) sequences from 271 strains of bacteria isolated from a semi-selective medium for Pseudomonas revealed that 69% (188/271) belonged to the P. syringae complex and represented 32 haplotypes in phylogroups 1, 2, 7, 9, 10, 13, 14 and 15. Strains within the P. syringae complex were identified in all eight lakes, and seven lakes contained ice+ strains. Partial 16S rDNA sequences were analyzed from a total of 492 pure cultures of bacteria isolated from non-selective medium. Nearly half (43.5%; 214/492) were associated with the genus Pseudomonas. Five of the lakes (ALT, GRU, GOS, GOL, and WOR) were all distinguished by high levels of Pseudomanas (p ≤ 0.001). HIN, the highest elevation lake, had the highest percentage of ice+ strains. Our work highlights the potential for uncovering new haplotypes of P. syringae in aquatic habitats, and the use of robotic technologies to sample and characterize microbial life in remote settings.

Detection and isolation of a new member of Burkholderiaceae-related endofungal bacteria from Saksenaea boninensis sp. nov., a new thermotolerant fungus in Mucorales

Thermotolerance in Mucorales (Mucoromycotina) is one of the factors to be opportunistic pathogens, causing mucormycosis. Among thermotolerant mucoralean fungi, Burkholderiaceae-related endobacteria (BRE) are rarely found and the known range of hosts is limited to Rhizopus spp. The phylogenetic divergence of BRE has recently expanded in other fungal groups such as Mortierellaceae spp. (Mortierellomycotina); however, it remains unexplored in Mucorales. Here, we found a thermotolerant mucoralean fungus obtained from a litter sample collected from Haha-jima Island in the Ogasawara (Bonin) Islands, Japan. The fungus was morphologically, phylogenetically, and physiologically characterized and proposed as a new species, Saksenaea boninensis sp. nov. Besides the fungal taxonomy, we also found the presence of BRE in isolates of this species by diagnostic PCR amplification of the 16S rRNA gene from mycelia, fluorescence microscopic observations, and isolation of the bacterium in pure culture. Phylogenetic analysis of the 16S rRNA gene of BRE revealed that it is distinct from all known BRE. The discovery of a culturable BRE lineage in the genus Saksenaea will add new insight into the evolutional origin of mucoralean fungus-BRE associations and emphasize the need to pay more attention to endofungal bacteria potentially associated with isolates of thermotolerant mucoralean fungi causing mucormycosis.

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.

The extent of nitrogen isotopic fractionation in rumen bacteria is associated with changes in rumen nitrogen metabolism.

Nitrogen use efficiency is an important index in ruminants and can be indirectly evaluated through the N isotopic discrimination between the animal and its diet (Δ15Nanimal-diet). The concentration and source of N may determine both the extent of the N isotopic discrimination in bacteria and N use efficiency. We hypothesised that the uptake and release of ammonia by rumen bacteria will affect the natural 15N enrichment of the bacterial biomass over their substrates (Δ15Nbacteria-substrate) and thereby further impacting Δ15Nanimal-diet. To test this hypothesis, two independent in vitro experiments were conducted using two contrasting N sources (organic vs inorganic) at different levels either in pure rumen bacteria culture incubations (Experiment #1) or in mixed rumen cultures (Experiment #2). In Experiment #1, tryptone casein or ammonium chloride were tested at low (1 mM N) and high (11.5 mM N) concentrations on three rumen bacterial strains (Fibrobacter succinogenes, Eubacterium limosum and Xylanibacter ruminicola) incubated in triplicate in anaerobic batch monocultures during 48h. In Experiment #2 mixed rumen cultures were incubated during 120 h with peptone or ammonium chloride at five different levels of N (1.5, 3, 4.5, 6 and 12-mM). In experiment #1, Δ15Nbacteria-substrate was lowest when the ammonia-consumer bacterium Fibrobacter succinogenes was grown on ammonium chloride, and highest when the proteolytic bacterial strain Xylanibacter ruminicola was grown on tryptone. In experiment #2, Δ15Nbacteria-substrate was lower with inorganic (ammonium chloride) vs organic (peptone) N source. A strong negative correlation between Δ15Nbacteria-substrate and Rikenellaceae_RC9_gut_group, a potential fibrolytic rumen bacterium, was detected. Together, our results showed that Δ15Nbacteria-substrate may change according to the balance between synthesis of microbial protein from ammonia versus non-ammonia N sources and confirm the key role of rumen bacteria as modulators of Δ15Nanimal-diet.