Culturable Bacterial Community Research Articles

Gut associated culturable bacterial community in intertidal polychaete worms (Annelida: Polychaeta), their characterization and implications in captive shrimp aquaculture

Polychaetes supplements play a crucial role in the dietary requirements of shrimps reared under captive culture. Due to their high demand, wild captured worms are used extensively as supplementary feed for the broodstocks. However, the gut microbiota composition of the polychaetes is rarely investigated. In the present study, the culturable fraction of gut microbiota of two native polychaete species, Marphysa madrasi and Namalycastis sp., that are currently used as live supplemental feed by shrimp brooders, were analysed. The culture-dependent technique yielded a total of 39 bacterial isolates, which grouped into 23 unique phylotypic clusters based on amplified ribosomal DNA restriction analysis (ARDRA) profiling. The 16S rRNA gene sequencing of these 23 gut isolates revealed bacterial communities with probiotic potential and a few shrimp and human pathogens. The gut-associated bacterial community is dominated by three bacterial phyla, the Firmicutes, Actinobacteria, and Proteobacteria, composed of 10 different genera. Moreover, there were differences in the bacterial communities between the two polychaetes investigated in this study. The Shannon, Simpson, Chao1 and Abundance-based Coverage Estimator (ACE) index revealed that M. madrasi have significantly higher species diversity and richness than Namalycastis sp. in the gut. Screening for hydrolytic enzyme production revealed several bacterial species with probiotic applications, such as Bacillus subtilis, B. licheniformis, B. pumilus, B. megaterium, and B. halotolerans. On the other hand, a few opportunistic human pathogens, such as B. cereus, Gordonia terrae, Microbacterium paraoxydans, Staphylococcus epidermidis, and Staphylococcus gallinarum, were also identified. Overall, the results of this study revealed that the bacterial assemblages associated with the gut of intertidal polychaete worms can serve as excellent probiotic candidates.

Suppression of rice seedling rot caused by Burkholderia glumae in nursery soils using culturable bacterial communities from organic farming systems

Suppression of rice seedling rot caused by Burkholderia glumae in nursery soils using culturable bacterial communities from organic farming systems

Spatio-temporal variations in culturable bacterial community associated with denitrification in the Arabian Sea oxygen minimum zone

ABSTRACT The Arabian Sea (AS) oxygen minimum zone (OMZ) is a site of intense denitrification, contributing to 20% of the global oceanic denitrification, playing a significant role in the nitrogen cycle. In this study, the structure and diversity of culturable bacterial communities inhabiting the water column of the AS OMZ were investigated through phylogenetic analysis and nitrate-utilizing ability was studied through culture-based studies. A total of 248 isolates collected during pre-monsoon and post-monsoon season were analysed for 16S rRNA gene sequences. Phylogenetic analysis revealed that the bacterial isolates belonged to 24 genera comprising class Gammaproteobacteria (79%), Firmicutes (18.15%), Bacteroidetes (1.61%) and Alphaproteobacteria (1.2%). Further, the ability of the organisms to reduce nitrate was tested by measuring nitrate reduction rate and nitrate reductase enzyme assay. Around 67% of the bacterial isolates were found to be nitrate reducers. The nitrate reduction rate ranged between 0.86–3.4 µM NO3 − day−1 while nitrate reductase activity varied from 0.01–1.32 U ml−1. The presence of a high number of nitrate-reducing bacteria in this region signifies a link between functional diversity and ecosystem biogeochemistry of the OMZ region of the Arabian Sea.

Characterization of persistent organic pollutants and culturable and non-culturable bacterial communities in pulp and paper sludge after secondary treatment

Due to the presence of various organic contaminants, improper disposal of pulp-paper wastewater poses harm to the environment and human health. In this work, pulp-paper sludge (PPS) after secondary treatment were collected from M/s Century Pulp-paper Mills in India, the chemical nature of the organic pollutants was determined after solvent extraction. All the isolates were able to produce lipase (6.34–3.93 U ml−1) which could account for the different fatty acids detected in the PPS. The dominant strains were in the classes of α and γ Proteobacteria followed by Firmicutes. The Shannon-Weiner diversity indexes for phylotype richness for the culturable and non-culturable bacterial community were 2.01 and 3.01, respectively, indicating the non-culturable bacterial strains has higher species richness and diversity compared to the culturable bacterial strains. However, the culturable strains had higher species evenness (0.94 vs 0.90). Results suggested only a few isolated strains were resistant to the POPs in the PPS, where as non-cultural bacteria survived by entering viable but non-cultural state. The isolated strains (Brevundimonas diminuta, Aeromonas punctata, Enterobacter hormaechei, Citrobacter braakii, Bacillus pumilus and Brevundimonas terrae) are known for their multidrug resistance but their tolerance to POPs have not previously been reported and deserved further investigation. The findings of this research established the presence of POPs which influence the microbial population. Tertiary treatment is recommended prior to the safe disposal of pulp paper mill waste into the environment.

Copper and zinc adsorption from bacterial biomass - possibility of low-cost industrial wastewater treatment

ABSTRACT The increasing interest of all stakeholders to achieve environmental protection with socioeconomic development puts pressure on industrial processes for less negative impact on the environment. The use of biomass for wastewater treatment has increased due to its low costs and technical feasibility. The present study aimed the use of biomass from a waste of known polluted area for the adsorption of Zn and Cu in a fixed-bed reactor. Samples were collected in Cubatão (Brazil) and cultivated in LB medium. Resulting cultivable bacterial communities were identified as Enterococcus faecalis and Pseudomonas aeruginosa. Adsorption experiments were performed varying the metallic ion concentration and the amount of biomass. Adsorption experiments showed efficiency rates up to 90%. As the concentration of metallic ions increased, the adsorption efficiency decreased, indicating that the active sites were saturated. Activated charcoal demonstrated lower adsorption rates than biomass. Elution process showed that HNO3 had better efficiency than HCl. Zn adsorption fitted better for Lineweaver–Burk model (Qmax = 200 mg/g of biomass), while Cu adsorption fitted better for Langmuir model (Qmax = 164 mg/g of biomass). Results here demonstrated that the adsorption of Zn and Cu simulating an industrial wastewater by the biomass from a contaminated area is technically feasible.

Culturable Bacterial Isolates from Arctic Soil shows High Biotechnological Potential

Polar microbiology remains as the most fascinating area of research which mainly focuses on exploration of psychrophilic organisms for having their cold-active enzymes of biotechnological potential. In this study, we have explored a culturable bacterial community and isolated 27 bacterial isolates with a different morphology from an unexplored site of Arctic region, for the possibility of identifying various active biomolecules. Screening of various isolates in a culture dependent manner helped us to identify strains capable of producing extracellular enzymes. The optimal growth parameters of most of the isolates are ranges between 18-22°C temperature, 3-5 days of incubation, 6-9 pH, and 3-5% (w/v) NaCl in LB media. It has also been found that among these isolates, 63% are able to produce lipase, 17% amylase, 7% xylanase and 7% isolates have responded for phosphatase activity but there are no isolates found for gelatinase and cellulase production ability. In addition, few isolates can also produce secretory protease, urease, β-galactosidase, etc. 16SrRNA gene sequence-based phylogeny revealed that the isolates belong to the genera of Psychrobacter, Planococcus, Halomonas, Arthrobacter, Oceanisphaera, Marinbacter, Pseudomonas, Algoriphagus. Strikingly, none of the Arctic isolates showed resistance towards commonly used antibiotics which indicates that the unexplored habitat is devoid of antibiotic exposure and so does the rise of antimicrobial resistance. The structure-function relationship of the isolated bioactive compounds from these isolates are the major focus of future research.

Antimicrobial activity of exometabolites of Paenibacillus polymyxa, isolated from endophytic community of winter wheat grain

In preliminary studies, a strain Paenibacillus polymyxa P6 possessing multiple plant growth-promoting (phosphate solubilization, oligonitrotrophy and production of heteroauxins) and antagonistic activities was isolated from grainresided cultivable bacterial endophytic community of winter wheat variety of the domestic selection Podolyanka with increased resistance to the causative agent of basal bacteriosis of grain crops Pseudomonas syringae pv. atrofaciens. The aim of this work was to study the antimicrobial effect of the exometabolites, produced by isolated strain, towards gram-negative phytopathogenic microorganisms using the method of deferred antagonism under the condition of cultivating the antagonistsc bacterium for 72 and 120 hours before inoculation of test cultures. Microorganisms stored in the collection of the D.K. Zabolotny Institute of Microbiology and Virology, NAS of Ukraine: Ralstonia solanocearum B-1109, Pectobacterium carotovora subsp. carotovora B-1077, Pseudomonas syringae pv. syringae B-1022, Pseudomonas syringae pv. syringae van Hall 1902 B-1027, Pseudomonas syringae pv. atrofaciens B-1011, Pseudomonas syringae pv. atrofaciens B-1013, as well as Erwinia amylovora ATCC 15580 were used as a test-cultures. Paenibacillus polymyxa P6 exometabolites were found to have a dose-dependent antimicrobial effect towards all studied microorganisms. The most pronounced inhibitory effect was registered against Erwinia amylovora ATCC 15580, Pseudomonas syringae pv. syringae B1022 and Ralstonia solanocearum B-1109: the diameter of the zone of no growth under the action of exometabolites produced for 120 hours are 25.72 ± 4.0 mm, 22.93 ± 2.0 mm and 20.30 ± 4.0 respectively. These results substantiate the expediency of further investigation of the composition and biological activity of the studied exometabolites in the perspective of developing biotechnological preparations.

Functional characterization of cultivable gut bacterial communities associated with rugose spiralling whitefly, Aleurodicus rugioperculatus Martin.

The online version contains supplementary material available at 10.1007/s13205-021-03081-3.

Manipulation of phyllosphere bacterial communities reversibly alters the plant microbiome and leaf traits in the field

Bacterial communities in the phyllosphere are shaped by host genotype and phenotype and spatio-temporal variation of the environment. In turn, bacteria have the potential for altering the plant phenotype. Field experiments can help to estimate bacterial effects on plant functional traits under natural conditions. We used a transplantation approach of culturable bacterial communities to explore how manipulation of leaf-associated microbial communities in two different successional stages within a glacier foreland can influence microbial composition and functional plant traits. Our study documents successional stage-specific variations in the composition of foliar bacterial communities and shifts therein throughout a season and between years. We show that cultured bacteria transferred between plant communities can alter diversity and composition of the microbiome on plant community level as well as species-specific functional plant traits of two selected plant species within one growing season. Furthermore, our results demonstrate a strong resilience of plant-associated bacterial communities and of plants in response to bacterial invaders. Our study illustrates that inoculation experiments in the field with naturally occurring microbial communities of wild plants are suited to investigate complex interactions between microbial communities, the environment, and plant traits.

Differential Tolerance to Calonectria pseudonaviculata of English Boxwood Plants Associated with the Complexity of Culturable Fungal and Bacterial Endophyte Communities.

Isolated boxwood endophytes have been demonstrated to effectively protect boxwood plants from infection by Calonectria pseudonaviculata (Cps). However, the roles of endophytes as communities in plant defense are not clear. Here, we demonstrated differential tolerance to Cps of English boxwood (Buxus sempervirens ‘Suffruticosa’), an iconic landscape plant and generally regarded as highly susceptible, and its link to endophyte complexity. Fifteen boxwood twig samples were collected in triplicates from three historic gardens—Colonial Williamsburg, George Washington’s Mount Vernon and River Farm, and Virginia Tech’s research farm in Virginia Beach in the summer and fall of 2019. A portion of individual samples was inoculated with Cps under controlled conditions. Significant differences in disease severity were observed among samples but not between the two seasons. Examining the endophyte cultures of the summer samples revealed that bacterial and fungal abundance was negatively and positively correlated with the disease severity. Nanopore metagenomics analysis on genomic DNA of the tolerant and susceptible group representatives confirmed the associations. Specifically, tolerant English boxwood plants had an endophyte community dominated by Bacilli and Betaproteobacteria, while susceptible ones had a distinct endophyte community dominated by Gammaproteobacteria, Actinobacteria, and diverse fungi. These findings may lead to boxwood health management innovations—devising and utilizing cultural practices to manipulate and increase the abundance and performance of beneficial endophytes for enhanced boxwood resistance to Cps.

Diversity of midgut bacteria in larvae and females of Aedes aegypti and Aedes albopictus from Gampaha District, Sri Lanka

BackgroundThe midgut microbiota of mosquitoes maintain basal immune activity and immune priming. In recent years, scientists have focused on the use of microbial communities for vector control interventions. In the present study, the midgut bacteria of larvae and adults of Aedes aegypti and Ae. albopictus were assessed using both field-collected and laboratory-reared mosquitoes from Sri Lanka.MethodsAdults and larvae of Ae. aegypti and Ae. albopictus were collected from three selected areas in Gampaha Medical Officer of Health area, Gampaha District, Western Province, Sri Lanka. Bacterial colonies isolated from mosquito midgut dissections were identified by PCR amplification and sequencing of partial 16S rRNA gene fragments.ResultsAdults and larvae of Ae. aegypti and Ae. albopictus harbored 25 bacterial species. Bacillus endophyticus and Pantoea dispersa were found more frequently in field-collected Ae. aegypti and Ae. albopictus adults, respectively. The midgut bacteria of Ae. aegypti and Ae. albopictus adults (X2 = 556.167, df = 72, P < 0.001) and larvae (X2 = 633.11, df = 66, P < 0.001) were significantly different. There was a significant difference among the bacterial communities between field-collected adults (X2 = 48.974, df = 10, P < 0.001) and larvae (X2 = 84.981, df = 10, P < 0.001). Lysinibacillus sphaericus was a common species in adults and larvae of laboratory-reared Ae. aegypti. Only P. dispersa occurred in the field-collected adults of Ae. aegypti and Ae. albopictus. Species belonging to genera Terribacillus, Lysinibacillus, Agromyces and Kocuria were recorded from Aedes mosquitoes, in accordance with previously reported results.ConclusionsThis study generated a comprehensive database on the culturable bacterial community found in the midgut of field-collected (Ae. aegypti and Ae. albopictus) and laboratory-reared (Ae. aegypti) mosquito larvae and adults from Sri Lanka. Data confirm that the midgut bacterial diversity in the studied mosquitoes varies according to species, developmental stage and strain (field vs laboratory).Graphical abstract

Environmental Antimicrobial Resistance in a Small Urban Mediterranean River: A Focus on Endemic Beta-Lactamases in Clinically Relevant Bacteria

Aquatic ecosystems subjected to anthropic pressures are likely hotspots for emergence or dissemination of antimicrobial resistant bacteria. The city of Montpellier is located on a Mediterranean climate watershed that undergoes strong demographic pressures. The aim of the study is to explore antimicrobial resistance, particularly those of clinical concern, in urban rivers flowing in this urban area. The method developed herein to explore antimicrobial resistance is based on cultural and molecular approaches completed by hydrological, hydrogeological, climatic, and physico-chemical data. Hospital vicinity and urbanization density significantly increase cultivable bacterial community, fecal bacteria from human origin, and prevalence of β-lactamases and extended-spectrum β-lactamases encoding-genes without an increase in 16S rDNA gene abundance. A total of 22 multidrug Enterobacterales have been isolated. All Escherichia coli (n = 10) and Klebsiella pneumoniae (n = 6) isolated on a made-house media carried β-lactamases genes, blaCTX-M being the most prevalent (87%), followed by blaTEM (56%) and blaSHV (37%), 56% of these strains carrying two or three of these genes. In urban settings, water quality and infectious risk are generally linked to wastewater treatment plants effluents. This study shows that running waters in urbanized area contribute to the dissemination of antimicrobial resistance, making these environments a reservoir for resistant bacteria with important consideration.

Cultivable rhizobacteria improve castor bean seedlings root and plant growth in Pb–Zn treated soil

Culturable bacteria are widely used in the remediation of heavy metal-contaminated soil associated with different plants. In this study, a pot experiment of castor bean (Ricinus communis L.) was performed to determine the effect of culturable bacterial communities on the growth of castor bean, as well as their response to the presence of Pb and Zn during the 21-day incubation. The results indicated that the inoculation of the cultivable bacterial communities promoted plant growth, whether Pb/Zn-contaminated or not, and a well-developed root system was also detected in the bacterial community after treatment. Under heavy metal stress, the root surface area of castor bean decreased significantly, but after inoculation, it was close to the level of the normal (uncontaminated) samples. Sequence analysis at the phylum and genus taxonomic levels illustrated 13 identified phyla and 125 genera were observed in the control and Pb/Zn-contaminated soil. The input of contaminants affected the bacterial community structure, suggesting that although Proteobacteria, Bacteroidetes, and Actinobacteria were the dominant phyla in the two samples, the Ensifer and Cupriavidus genera were decreased in contaminated soil. However, Arcticibacter, a phosphate-solubilizing bacterium, was enriched by the Pb/Zn treatment. Compared with the control group, Pb and Zn exposure in the treatment group resulted in a new community structure. A microflora consisting of a number of microorganisms undergoing a long duration period of adaptation and symbiosis can possess systematic functions with high stabilities, so it has considerably high potential in intensifying the effect of phytoremediation.

Genome-Inferred Correspondence between Phylogeny and Metabolic Traits in the Wild Drosophila Gut Microbiome.

Annotated genome sequences provide valuable insight into the functional capabilities of members of microbial communities. Nevertheless, most studies on the microbiome in animal guts use metagenomic data, hampering the assignment of genes to specific microbial taxa. Here, we make use of the readily culturable bacterial communities in the gut of the fruit fly Drosophila melanogaster to obtain draft genome sequences for 96 isolates from wild flies. These include 81 new de novo assembled genomes, assigned to three orders (Enterobacterales, Lactobacillales, and Rhodospirillales) with 80% of strains identified to species level using average nucleotide identity and phylogenomic reconstruction. Based on annotations by the RAST pipeline, among-isolate variation in metabolic function partitioned strongly by bacterial order, particularly by amino acid metabolism (Rhodospirillales), fermentation, and nucleotide metabolism (Lactobacillales) and arginine, urea, and polyamine metabolism (Enterobacterales). Seven bacterial species, comprising 2–3 species in each order, were well-represented among the isolates and included ≥5 strains, permitting analysis of metabolic functions in the accessory genome (i.e., genes not present in every strain). Overall, the metabolic function in the accessory genome partitioned by bacterial order. Two species, Gluconobacter cerinus (Rhodospirillales) and Lactiplantibacillus plantarum (Lactobacillales) had large accessory genomes, and metabolic functions were dominated by amino acid metabolism (G. cerinus) and carbohydrate metabolism (La. plantarum). The patterns of variation in metabolic capabilities at multiple phylogenetic scales provide the basis for future studies of the ecological and evolutionary processes shaping the diversity of microorganisms associated with natural populations of Drosophila.

Beneficial traits of root endophytes and rhizobacteria associated with plants growing in phytomanaged soils with mixed trace metal-polycyclic aromatic hydrocarbon contamination

The diversity of cultivable bacteria associated with plants from phytomanaged soils with mixed trace metal (TM) and polycyclic aromatic hydrocarbon (PAH) contamination in Pierrelaye (France) was evaluated. The emphasis was on the cultivable bacterial community since the overall objective is to obtain inoculants to improve the remediation of this type of contaminated site. Root endophytic and rhizosphere soil bacterial counts were determined, and isolates were pooled by amplified rDNA restriction analysis and identified by 16S rDNA sequencing. Isolates were further characterized for the production of plant growth-promoting (PGP) substances, and resistance to TM. The selected strains were evaluated for their ability to degrade PAHs. The potential of cell-free microbial supernatant to increase the mobilisation of PAHs from the polluted soil of Pierrelaye was also evaluated. Proteobacteria and Actinobacteria dominated the collection of isolates, and differences in taxonomic diversity were observed between plant species (Populus or Zea mays) and depending on the remediation treatment (Populus inoculation with mycorrhizae or Populus intercropping with Alnus). The majority of isolates exhibited at least one of the tested PGP traits, as well as resistance to more than one TM. Several rhizosphere, endophyte and even one bulk soil isolate showed high rates of fluoranthene and pyrene reduction. The endophyte Rhizobium strain MR28 isolated from maize and degrading pyrene produced bioemulsifying molecules capable of improving the availability of PAHs from the soil of Pierrelaye. A selection of the most interesting strains was made for further re-inoculation experiments in order to assess their potential in rhizoremediation processes.

Phylogenetic diversity of culturable marine bacteria from sediments underlying the oxygen minimum zone of the Arabian Sea and their role in nitrate reduction

AbstractThe eastern Arabian Sea has a unique and permanent oxygen minimum zone (OMZ) extending along the western continental margin of India. The Arabian Sea OMZ is a site of intense denitrification, contributing to 20% of the global oceanic denitrification, playing a significant role in the nitrogen cycle. This study reveals the members of the culturable marine bacterial communities thriving and functioning in the sediment underlying the Arabian Sea OMZ, through 16S rDNA phylogenetic analysis and elucidating their nitrate reduction potential. Phylogenetic analyses revealed that these cultured bacteria distributed into five phyla, viz. Firmicutes (45.7%) Gammaproteobacteria (36.84%), Actinobacteria (8.7%), Bacteroidetes (5.26%), and Alphaproteobacteria (3.5%). The presence of denitrification genes such as narG, nirS, and nosZ in the cultured bacteria (39%) explains their importance in this process. Present study on the diversity and distribution of bacterial communities in the OMZ surface sediment and their probable role in the nitrogen cycle will provide insight into the microbial biogeochemical processes occurring in this region.

Shifts in the structure of rhizosphere bacterial communities of avocado after Fusarium dieback

The rhizosphere microbiome is critical for plant growth and protection against plant pathogens. However, rhizosphere microbial communities are likely to be restructured upon plant infection by fungal pathogens. Our objective was to determine the shifts in rhizosphere bacterial communities of avocado trees (Persea americana Mill.) after Fusarium dieback (FD), a disease triggered by the symbiotic fungi of invasive ambrosia beetles (Euwallacea kuroshio and Euwallacea sp. nr. fornicatus), using 16S rDNA gene amplicon sequencing and a culture-dependent approach. Rhizosphere soil samples were collected from five asymptomatic and five FD-symptomatic avocado trees in a Californian orchard. Sequence analysis showed that diversity metrics of the rhizosphere bacterial communities associated with asymptomatic avocado trees were larger than those of communities from FD-symptomatic trees. Moreover, FD produced significant shifts in rhizobacterial community structure, which were mainly caused by rare OTUs. Bacterial taxa such as Armatimonadetes, Sporocytophaga or Cellvibrio were exclusively associated with the rhizosphere of asymptomatic trees and may act as an insurance mechanism against fungal invasions. Conversely, genera such as Myxococcus or Lysobacter, which have been described as effective biocontrol agents against Fusarium oxysporum, Colletotrichum gloeosporioides or Rhizoctonia spp., among other phytopathogens, were only found in the rhizosphere of FD-symptomatic trees. The culturable bacterial communities in the rhizosphere of both FD-symptomatic and asymptomatic trees were dominated by isolates from the Bacillus and Pseudomonas genera, indicating that potential biocontrol agents against FD may be isolated from healthy and diseased avocado trees. Altogether, our results showed that FD elicited shifts in the avocado rhizosphere microbiome, which could potentially affect soil microbial processes, and provide a basis for the selection of biocontrol agents that could be used for FD prevention.

Mono- and multispecies biofilms from a crustose coralline alga induce settlement in the scleractinian coral Leptastrea purpurea

Microorganisms have been reported to induce settlement in various marine invertebrate larvae but their specificity of inductive capacities for the settlement of coral larvae remains poorly understood. In this study, we isolated 56 microbial strains from the crustose coralline alga (CCA) Hydrolithon reinboldii using five different media either with or without additional antibiotics and/or spiked CCA extract. We tested the isolates for their potential to induce settlement behavior in larvae of the brooding scleractinian coral Leptastrea purpurea. From these 56 CCA-associated microbial strains, we identified six bacterial classes and 18 families. The culturable bacterial community associated with H. reinboldii was dominated by Gammaproteobacteria, Actinobacteria, and Alphaproteobacteria while the Illumina MiSeq analysis showed that the culture-independent bacterial community was dominated by Gammaproteobacteria, Alphaproteobacteria, and Flavobacteria. Furthermore, we found no correlation between inductive settlement capacities and phylogenetic relationships. Instead, settlement behavior of L. purpurea larvae was induced by specific isolated species. Strains #1792 (Pseudovibrio denitrificans), #1678 (Acinetobacter pittii), #1633 (Pseudoalteromonas phenolica), #1772 (Marine bacterium LMG1), #1721 (Microbulbifer variabilis), and #1783 (Pseudoalteromonas rubra) induced settlement behavior in coral larvae at mostly high and significant levels (≥ 40%) but the remaining isolates strongly varied in their activity. Multispecies biofilms consisting of four strains (#1792, #1678, #1633, and #1721) were observed to synergistically increase settlement behavior levels (> 90%); however, the addition of #1772 to the multispecies biofilms negatively affected coral larvae and resulted in a total loss of inducing activity. The findings provide new insights into the role of bacteria in the settlement process of scleractinian corals and may help to identify the true nature of bacteria-derived morphogenic cues.

Effect of substitution of chemical fertilizer by bioinoculants on plant performance and rhizospheric bacterial community: case study with Cajanus cajan.

Improper nutrient management is one of the major limitations linked with cultivation of Cajanus cajan. This calls for an urgent need for a promising alternative, employing both bioinoculants and chemical fertilizer. Present study attempted to understand the impact of bioinoculants {Azotobacter chroococcum, Bacillus megaterium, and Pseudomonas fluorescens (ABP)} as their mono-inoculations, triple-inoculation, and their combination with different doses of fertilizer on (a) plant parameters, (b) soil nitrogen (N) economy, (c) resident bacterial community, (d) genes and transcripts involved in N cycle, and to evaluate the extent to which fertilizer could be replaced by ABP without compromising on grain yield. Bradyrhizobium sp. was used in all the treatments (as it was recommended for C. cajan). Combined application of bioinoculants and 75% of recommended dose of fertilizer (RDF) led to 1.28-fold enhancement in grain yield as compared to RDF alone. Apart fromexerting a positive impact on grain yield, the combined application of ABP and fertilizer led to an improvement in soil fertility, and modified the culturablerhizospheric bacterial community involved in N cycle. Integrated use of bioinoculants and fertilizer led to better N substrate utilization and hence, metabolic diversity when compared with application of fertilizer alone. An increase in the transcripts of nifH gene at the harvest stagein the soil treated with ABP alone and its combination with fertilizer, over individual treatment withfertilizer was observed. The combined use of ABP and fertilizer shaped the resident bacterial community towards a more beneficial community, which helped in increasing soil nitrogen turnover and hence, soil fertility as a whole.

Metagenomic Characterization of the Culturable Bacterial Community Structure of Tapuy, a Philippine Indigenous Rice Wine, Reveals Significant Presence of Potential Probiotic Bacteria

Metagenomic Characterization of the Culturable Bacterial Community Structure of Tapuy, a Philippine Indigenous Rice Wine, Reveals Significant Presence of Potential Probiotic Bacteria