Project description:Bdellovibrio-and-like organisms (BALOs) are Gram-negative, predatory bacteria that inhabit terrestrial, freshwater and saltwater environments. They have been detected primarily by culture-dependent methods which have limitations. In this study, diversity and community structure of BALOs in freshwater and saltwater samples were characterized by 16S rRNA gene pyrosequencing with specific BALO group primers. Novel Bacteriovorax 16S rDNA sequences were found both in saltwater enrichment cultures and in situ environmental samples, but no new operational taxonomic units were detected in the freshwater samples. The results revealed unexpected diversity of BALOs and advance understanding of the similarities and differences between Bdellovibrio and Bacteriovorax diversity and distribution in the environment.
Project description:Bdellovibrio and like organisms are abundant environmental parasitoids of prokaryotes that show diverse predation strategies. The vast majority of studied Bdellovibrio bacteria and like organisms deploy intraperiplasmic replication inside the prey cell, while few isolates with smaller genomes consume their prey from the outside in an epibiotic manner. The novel parasitoid "Candidatus Bdellovibrio qaytius" was isolated from a eutrophic freshwater pond in British Columbia, where it was a continual part of the microbial community. "Ca Bdellovibrio qaytius" was found to preferentially prey on the betaproteobacterium Paraburkholderia fungorum without entering the periplasm. Despite its epibiotic replication strategy, "Ca Bdellovibrio" encodes a large genomic complement more similar to that of complex periplasmic predators. Functional genomic annotation further revealed several biosynthesis pathways not previously found in epibiotic predators, indicating that "Ca Bdellovibrio" represents an intermediate phenotype and at the same time narrowing down the genomic complement specific to epibiotic predators. In phylogenetic analysis, "Ca Bdellovibrio qaytius" occupies a widely distributed, but poorly characterized, basal cluster within the genus Bdellovibrio This suggests that epibiotic predation might be a common predation type in nature and that epibiotic predation could be the ancestral predation type in the genus.IMPORTANCE Bdellovibrio and like organisms are bacteria that prey on other bacteria and are widespread in the environment. Most of the known Bdellovibrio species enter the space between the inner and outer prey membrane, where they consume their prey cells. However, one Bdellovibrio species has been described that consumes its prey from the outside. Here, we describe "Ca Bdellovibrio qaytius," a novel member of the genus Bdellovibrio that also remains outside the prey cell throughout its replication cycle. Unexpectedly, the genome of "Ca Bdellovibrio" is much more similar to the genomes of intracellular predators than to the species with a similar life cycle. Since "Ca Bdellovibrio" is also a basal representative of this genus, we hypothesize that extracellular predation could be the ancestral predation strategy.
Project description:A growing body of data suggests that the microbiome of a species can vary considerably from individual to individual, but the reasons for this variation-and the consequences for the ecology of these communities-remain only partially explained. In mammals, the emerging picture is that the metabolic state and immune system status of the host affect the composition of the microbiome, but quantitative ecological microbiome studies are challenging to perform in higher organisms. Here, we show that these phenomena can be quantitatively analyzed in the tractable nematode host <i>Caenorhabditis elegans</i> Mutants in innate immunity, in particular the DAF-2/insulin growth factor (IGF) pathway, are shown to contain a microbiome that differs from that of wild-type nematodes. We analyzed the underlying basis of these differences from the perspective of community ecology by comparing experimental observations to the predictions of a neutral sampling model and concluded that fundamental differences in microbiome ecology underlie the observed differences in microbiome composition. We tested this hypothesis by introducing a minor perturbation into the colonization conditions, allowing us to assess stability of communities in different host strains. Our results show that altering host immunity changes the importance of interspecies interactions within the microbiome, resulting in differences in community composition and stability that emerge from these differences in host-microbe ecology.<b>IMPORTANCE</b> Here, we used a <i>Caenorhabditis elegans</i> microbiome model to demonstrate how genetic differences in innate immunity alter microbiome composition, diversity, and stability by changing the ecological processes that shape these communities. These results provide insight into the role of host genetics in controlling the ecology of the host-associated microbiota, resulting in differences in community composition, successional trajectories, and response to perturbation.
Project description:<h4>Objectives</h4><i>Bdellovibrio</i>-and-like organisms (BALOs) are predatory prokaryotes that attack and kill other Gram-negative bacteria for growth and reproduction. This study describes the isolation, identification, biological properties, and bacteriolytic activity of the first <i>Bdellovibrio</i> <i>bacteriovorus</i> with a broad prey range from Iran.<h4>Materials and methods</h4>One BALO strain with high predatory potency was isolated from the rhizosphere soil using Enteropathogenic <i>Escherichia coli</i> as prey. It was identified and designated as <i>Bdellovibrio bacteriovorus</i> strain SOIR-1 through plaque assays, transmission electron microscopy (TEM), <i>Bdellovibrio</i>-specific PCRs, and 16S rRNA gene sequence analysis. Biological characterization and analysis of bacteriolytic activity were also performed.<h4>Results</h4>TEM and <i>Bdellovibrio</i>-specific PCRs confirmed that the strain SOIR-1 belongs to the genus <i>Bdellovibrio</i>. Analysis of the 16S rRNA gene sequence revealed its close phylogenetic relationship with strains of <i>Bdellovibrio bacteriovorus</i>. The strain SOIR-1 grew within the temperature range of 25-37 <sup>°</sup>C and the pH range of 6.0-8.0, with the optimal predatory activity at 30 <sup>°</sup>C and pH 7.4. It had the highest and lowest bacteriolytic activity toward <i>Shigella dysenteriae</i> and <i>Pseudomonas aeruginosa</i> with a killing rate of 89.66% and 74.83%, respectively.<h4>Conclusion</h4>Considering the hypothesis of bdellovibrios heterogeneity, identification of new isolates contributes to a deeper understanding of their diversity, their ecological roles, and their promising potential as living antibiotics or biocontrol agents. Bdellovibrios with broad bacteriolytic nature has not previously been reported in sufficient detail from Iran. The results of this study showed the great potential of native <i>B. bacteriovorus</i> strain SOIR-1 in the control and treatment of diseases caused by pathogenic <i>Enterobacteriaceae</i>.
Project description:<h4>Background</h4>Bacteria adapted to live within animals can protect their hosts against harmful infections. Beyond antagonism with pathogens, a 'defensive' bacterial symbiont could engage in additional interactions with other colonizing micro-organisms. A single bacterium might thus have cascading ecological impacts on the whole microbiome that are rarely investigated. Here, we assess the role of a defensive symbiont as a driver of host-associated microbiota composition by using a bacterial species (Enterococcus faecalis) that was previously experimentally adapted to a nematode host model (Caenorhabditis elegans).<h4>Results</h4>An analysis of 16S rRNA data from C. elegans exposed to E. faecalis and subsequently reared in soil, reveal that symbiont adaptation to host environment or its protective potential had minimal impact on microbiota diversity. Whilst the abundance of Pseudomonas was higher in the microbiota of hosts with protective E.faecalis (and another protective species tested), a few other genera - including Serratia and Salinispora - were less abundant in hosts colonized by all E. faecalis strains. In addition, the protective effect of E. faecalis against virulent Staphylococcus aureus pathogens was maintained despite multi-species interactions within the microbiota.<h4>Conclusions</h4>Our results reveal the degree to which a new, evolving symbiont can colonise and maintain pathogen-resistance with minimal disruption to host microbiota diversity.
Project description:Bdellovibrio bacteriovorus is a bacterium which preys upon and kills Gram-negative bacteria, including the zoonotic pathogens Escherichia coli and Salmonella. Bdellovibrio has potential as a biocontrol agent, but no reports of it being tested in living animals have been published, and no data on whether Bdellovibrio might spread between animals are available. In this study, we tried to fill this knowledge gap, using B. bacteriovorus HD100 doses in poultry with a normal gut microbiota or predosed with a colonizing Salmonella strain. In both cases, Bdellovibrio was dosed orally along with antacids. After dosing non-Salmonella-infected birds with Bdellovibrio, we measured the health and well-being of the birds and any changes in their gut pathology and culturable microbiota, finding that although a Bdellovibrio dose at 2 days of age altered the overall diversity of the natural gut microbiota in 28-day-old birds, there were no adverse effects on their growth and well-being. Drinking water and fecal matter from the pens in which the birds were housed as groups showed no contamination by Bdellovibrio after dosing. Predatory Bdellovibrio orally administered to birds that had been predosed with a gut-colonizing Salmonella enterica serovar Enteritidis phage type 4 strain (an important zoonotic pathogen) significantly reduced Salmonella numbers in bird gut cecal contents and reduced abnormal cecal morphology, indicating reduced cecal inflammation, compared to the ceca of the untreated controls or a nonpredatory ?pilA strain, suggesting that these effects were due to predatory action. This work is a first step to applying Bdellovibrio therapeutically for other animal, and possibly human, infections.
Project description:Microbes drive a variety of ecosystem processes and services, but many of them remain largely unexplored because of a lack of knowledge on both the diversity and functionality of some potentially crucial microbiological compartments. This is the case with and within the group of bacterial predators collectively known as Bdellovibrio and like organisms (BALOs). Here, we report the abundance, distribution, and diversity of three families of these obligate predatory Gram-negative bacteria in three perialpine lakes (Lakes Annecy, Bourget, and Geneva). The study was conducted at different depths (near-surface versus 45 or 50?m) from August 2015 to January 2016. Using PCR-denaturing gradient gel electrophoresis (PCR-DGGE) and cloning-sequencing approaches, we show that the diversity of BALOs is relatively low and very specific to freshwaters or even the lakes themselves. While the Peredibacteraceae family was represented mainly by a single species (Peredibacter starrii), it could represent up to 7% of the total bacterial cell abundances. Comparatively, the abundances of the two other families (Bdellovibrionaceae and Bacteriovoracaceae) were significantly lower. In addition, the distributions in the water column were very different between the three groups, suggesting various life strategies/niches, as follows: Peredibacteraceae dominated near the surface, while Bdellovibrionaceae and Bacteriovoracaceae were more abundant at greater depths. Statistical analyses revealed that BALOs seem mainly to be driven by depth and temperature. Finally, this original study was also the opportunity to design new quantitative PCR (qPCR) primers for Peredibacteraceae quantification.IMPORTANCE This study highlights the abundance, distribution, and diversity of a poorly known microbial compartment in natural aquatic ecosystems, the Bdellovibrio and like organisms (BALOs). These obligate bacterial predators of other bacteria may have an important functional role. This study shows the relative quantitative importance of the three main families of this group, with the design of a new primer pair, and their diversity. While both the diversity and the abundances of these BALOs were globally low, it is noteworthy that the abundance of the Peredibacteraceae could reach important values.
Project description:Studies in model organisms have yielded considerable insights into the etiology of disease and our understanding of evolutionary processes. Caenorhabditis elegans is among the most powerful model organisms used to understand biology. However, C. elegans is not used as extensively as other model organisms to investigate how natural variation shapes traits, especially through the use of genome-wide association (GWA) analyses. Here, we introduce a new platform, the C. elegans Natural Diversity Resource (CeNDR) to enable statistical genetics and genomics studies of C. elegans and to connect the results to human disease. CeNDR provides the research community with wild strains, genome-wide sequence and variant data for every strain, and a GWA mapping portal for studying natural variation in C. elegans Additionally, researchers outside of the C. elegans community can benefit from public mappings and integrated tools for comparative analyses. CeNDR uses several databases that are continually updated through the addition of new strains, sequencing data, and association mapping results. The CeNDR data are accessible through a freely available web portal located at http://www.elegansvariation.org or through an application programming interface.
Project description:Bdellovibrio spp. are predatory bacteria with great potential as antimicrobial agents. Studies have shown that members of the genus Bdellovibrio exhibit peculiar characteristics that influence their ecological adaptations. In this study, whole genomes of two different Bdellovibrio spp. designated SKB1291214 and SSB218315 isolated from soil were sequenced. The core genes shared by all the Bdellovibrio spp. considered for the pangenome analysis including the epibiotic B. exovorus were 795. The number of unique genes identified in Bdellovibrio spp. SKB1291214, SSB218315, W, and B. exovorus JJS was 1343, 113, 857, and 1572, respectively. These unique genes encode hydrolytic, chemotaxis, and transporter proteins which might be useful for predation in the Bdellovibrio strains. Furthermore, the two Bdellovibrio strains exhibited differences based on the % GC content, amino acid identity, and 16S rRNA gene sequence. The 16S rRNA gene sequence of Bdellovibrio sp. SKB1291214 shared 99% identity with that of an uncultured Bdellovibrio sp. clone 12L 106 (a pairwise distance of 0.008) and 95-97% identity (a pairwise distance of 0.043) with that of other culturable terrestrial Bdellovibrio spp., including strain SSB218315. In Bdellovibrio sp. SKB1291214, 174?bp sequence was inserted at the host interaction (hit) locus region usually attributed to prey attachment, invasion, and development of host independent Bdellovibrio phenotypes. Also, a gene equivalent to Bd0108 in B. bacteriovorus HD100 was not conserved in Bdellovibrio sp. SKB1291214. The results of this study provided information on the genetic characteristics and diversity of the genus Bdellovibrio that can contribute to their successful applications as a biocontrol agent.
Project description:Host genetic landscapes can shape microbiome assembly in the animal gut by contributing to the establishment of distinct physiological environments. However, the genetic determinants contributing to the stability and variation of these microbiome types remain largely undefined. Here, we use the free-living nematode Caenorhabditis elegans to identify natural genetic variation among wild strains of C. elegans that drives assembly of distinct microbiomes. To achieve this, we first established a diverse model microbiome that represents the strain-level phylogenetic diversity naturally encountered by C. elegans in the wild. Using this community, we show that C. elegans utilizes immune, xenobiotic, and metabolic signaling pathways to favor the assembly of different microbiome types. Variations in these pathways were associated with enrichment for specific commensals, including the Alphaproteobacteria Ochrobactrum. Using RNAi and mutant strains, we showed that host selection for Ochrobactrum is mediated specifically by host insulin signaling pathways. Ochrobactrum recruitment is blunted in the absence of DAF-2/IGFR and modulated by the competitive action of insulin signaling transcription factors DAF-16/FOXO and PQM-1/SALL2. Further, the ability of C. elegans to enrich for Ochrobactrum as adults is correlated with faster animal growth rates and larger body size at the end of development. These results highlight a new role for the highly conserved insulin signaling pathways in the regulation of gut microbiome composition in C. elegans.