A proposal for the reclassification of Bdellovibrio stolpii and Bdellovibrio starrii into a new genus, Bacteriovorax gen. nov. as Bacteriovorax stolpii comb. nov. and Bacteriovorax starrii comb. nov., respectively. (1/117)

Bdellovibrios are unique bacteria with the ability to prey upon a wide variety of susceptible Gram-negative bacteria. Micro-organisms exhibiting this trait have been included in the genus Bdellovibrio despite their isolation from diverse habitats and relatively unstudied taxonomic relatedness. In this study, 16S rDNA sequences were compared from known terrestrial Bdellovibrio species, Bdellovibrio bacteriovorus 100T, Bdellovibrio stolpii Uki2T and Bdellovibrio starrii A3.12T in order to study their phylogenetic relationship. The two sequences from B. stolpii Uki2T and B. starrii A3.12T were 90.0% similar to each other but exhibited only 81.7% and 81.2% similarity, respectively to B. bacteriovorus 100T. Phylogenetic analysis indicated that B. bacteriovorus 100T clustered in a separate clade from B. starrii A3.12T and B. stolpii Uki2T, demonstrating only a distant relationship between B. bacteriovorus 100T and the other two recognized type species. DNA-DNA hybridization experiments also demonstrated <4% hybridization between these three species. On the basis of the results obtained from the phylogenetic analysis and DNA-DNA hybridization studies, it is proposed that B. stolpii Uki2T and B. starrii A3.12T should be transferred to a new genus, Bacteriovorax gen. nov. as Bacteriovorax stolpii comb. nov. and Bacteriovorax starrii comb. nov., respectively. It is also proposed that the type species for the new genus Bacteriovorax should be Bacteriovorax stolpii comb. nov.  (+info)

Prey range characterization, ribotyping, and diversity of soil and rhizosphere Bdellovibrio spp. isolated on phytopathogenic bacteria. (2/117)

Thirty new Bdellovibrio strains were isolated from an agricultural soil and from the rhizosphere of plants grown in that soil. Using a combined molecular and culture-based approach, we found that the soil bdellovibrios included subpopulations of organisms that differed from rhizosphere bdellovibrios. Thirteen soil and seven common bean rhizosphere Bdellovibrio strains were isolated when Pseudomonas corrugata was used as prey; seven and two soil strains were isolated when Erwinia carotovora subsp. carotovora and Agrobacterium tumefaciens, respectively, were used as prey; and one tomato rhizosphere strain was isolated when A. tumefaciens was used as prey. In soil and in the rhizosphere, depending on the prey cells used, the concentrations of bdellovibrios were between 3 x 10(2) to 6 x 10(3) and 2.8 x 10(2) to 2.3 x 10(4) PFU g(-1). A prey range analysis of five soil and rhizosphere Bdellovibrio isolates performed with 22 substrate species, most of which were plant-pathogenic and plant growth-enhancing bacteria, revealed unique utilization patterns and differences between closely related prey cells. An approximately 830-bp fragment of the 16S rRNA genes of all of the Bdellovibrio strains used was obtained by PCR amplification by using a Bdellovibrio-specific primer combination. Soil and common bean rhizosphere strains produced two and one restriction patterns for this PCR product, respectively. The 16S rRNA genes of three soil isolates and three root-associated isolates were sequenced. One soil isolate belonged to the Bdellovibrio stolpii-Bdellovibrio starrii clade, while all of the other isolates clustered with Bdellovibrio bacteriovorus and formed two distantly related, heterogeneous groups.  (+info)

Predatory prokaryotes: predation and primary consumption evolved in bacteria. (3/117)

Two kinds of predatory bacteria have been observed and characterized by light and electron microscopy in samples from freshwater sulfurous lakes in northeastern Spain. The first bacterium, named Vampirococcus, is Gram-negative and ovoidal (0.6 micrometer wide). An anaerobic epibiont, it adheres to the surface of phototrophic bacteria (Chromatium spp.) by specific attachment structures and, as it grows and divides by fission, destroys its prey. An important in situ predatory role can be inferred for Vampirococcus from direct counts in natural samples. The second bacterium, named Daptobacter, is a Gram-negative, facultatively anaerobic straight rod (0.5 x 1.5 micrometers) with a single polar flagellum, which collides, penetrates, and grows inside the cytoplasm of its prey (several genera of Chromatiaceae). Considering also the well-known case of Bdellovibrio, a Gram-negative, aerobic curved rod that penetrates and divides in the periplasmic space of many chemotrophic Gram-negative bacteria, there are three types of predatory prokaryotes presently known (epibiotic, cytoplasmic, and periplasmic). Thus, we conclude that antagonistic relationships such as primary consumption, predation, and scavenging had already evolved in microbial ecosystems prior to the appearance of eukaryotes. Furthermore, because they represent methods by which prokaryotes can penetrate other prokaryotes in the absence of phagocytosis, these associations can be considered preadaptation for the origin of intracellular organelles.  (+info)

Microviridae, a family divided: isolation, characterization, and genome sequence of phiMH2K, a bacteriophage of the obligate intracellular parasitic bacterium Bdellovibrio bacteriovorus. (4/117)

A novel single-stranded DNA phage, phiMH2K, of Bdellovibrio bacteriovorus was isolated, characterized, and sequenced. This phage is a member of the Microviridae, a family typified by bacteriophage phiX174. Although B. bacteriovorus and Escherichia coli are both classified as proteobacteria, phiMH2K is only distantly related to phiX174. Instead, phiMH2K exhibits an extremely close relationship to the Microviridae of Chlamydia in both genome organization and encoded proteins. Unlike the double-stranded DNA bacteriophages, for which a wide spectrum of diversity has been observed, the single-stranded icosahedral bacteriophages appear to fall into two distinct subfamilies. These observations suggest that the mechanisms driving single-stranded DNA bacteriophage evolution are inherently different from those driving the evolution of the double-stranded bacteriophages.  (+info)

16S rDNA sequence analysis of environmental Bdellovibrio-and-like organisms (BALO) reveals extensive diversity. (5/117)

Bdellovibrio-and-like organisms (BALO) are Gram-negative, predatory bacteria that inhabit terrestrial, freshwater and salt-water environments. Historically, these organisms have been classified together despite documented genetic differences between isolates. The genetic diversity of these microbes was assessed by sequencing the 16S rRNA gene. Primers that selectively amplify predator 16S rDNA, and not contaminating prey DNA, were utilized to study 17 freshwater and terrestrial and nine salt-water BALO isolates. When the 16S rDNA sequences were compared with representatives of other bacterial classes, 25 of the 26 BALO isolates clustered into two groups. One group, supported 100% by bootstrap analysis, included all of the Bdellovibrio bacteriovorus isolates. Each member of this group was isolated from either a freshwater or terrestrial source. The genetic distance between these isolates was less than 12%. The other group, supported 94% by bootstrap analysis, includes Bacteriovorax starrii, Bacteriovorax stolpii and the salt-water isolates. The salt-water isolates form a subgroup (83% by bootstrap) and differ within the subgroup by less than 110%. This observation implies that the salt-water isolates arose from Bacteriovorax progenitors. The difference between isolates in different clades is over 17%, a quantity similar to differences between bacterial species in different classes. However, both the Bdellovibrio and Bacteriovorax clades were closest to other representatives of the delta-Proteobacteria using maximum-likelihood. One freshwater isolate, James Island, was distinct from all other BALO (> 19%), but differed from Pseudomonas putida, a member of the gamma-Proteobacteria, by only 3%. Thus, by 16S rDNA sequence analysis, the BALO appear to have multiple origins, contrary to the unified taxonomic grouping based on morphology and natural history. These observations are consistent with the need to review and revise the taxonomy of these organisms.  (+info)

Investigations into the life cycle of the bacterial predator Bdellovibrio bacteriovorus 109J at an interface by atomic force microscopy. (6/117)

Atomic force microscopy was used to image Bdellovibrio bacteriovorus 109J, a gram-negative bacterial predator that consumes a variety of other gram-negative bacteria. In predator-prey communities grown on filters at hydrated air-solid interfaces, repeated cycles of hunting, invasion, growth, and lysis occurred readily even though the cells were limited to near two-dimensional movement. This system allowed us to image the bacteria directly without extensive preparation or modification, and many of the cells remained alive during imaging. Presented are images of the life cycle in two species of prey organisms, both Escherichia coli (a small prey bacterium that grows two-dimensionally on a surface) and Aquaspirillum serpens (a large prey bacterium that grows three-dimensionally on a surface), including high-resolution images of invaded prey cells called bdelloplasts. We obtained evidence for multiple invasions per prey cell, as well as significant heterogeneity in morphology of bdellovibrios. Mutant host-independent bdellovibrios were observed to have flagella and to excrete a coating that causes the predators to clump together on a surface. Most interestingly, changes in the texture of the cell surface membranes were measured during the course of the invasion cycle. Thus, coupled with our preparation method, atomic force microscopy allowed new observations to be made about Bdellovibrio at an interface. These studies raise important questions about the ways in which bacterial predation at interfaces (air-solid or liquid-solid) may be similar to or different from predation in solution.  (+info)

The obligate predatory Bdellovibrio bacteriovorus possesses a neutral lipid A containing alpha-D-Mannoses that replace phosphate residues: similarities and differences between the lipid As and the lipopolysaccharides of the wild type strain B. bacteriovorus HD100 and its host-independent derivative HI100. (7/117)

Bdellovibrio bacteriovorus are predatory bacteria that penetrate Gram-negative bacteria and grow intraperiplasmically at the expense of the prey. It was suggested that B. bacteriovorus partially degrade and reutilize lipopolysaccharide (LPS) of the host, thus synthesizing an outer membrane containing structural elements of the prey. According to this hypothesis a host-independent mutant should possess a chemically different LPS. Therefore, the lipopolysaccharides of B. bacteriovorus HD100 and its host-independent derivative B. bacteriovorus HI100 were isolated and characterized by SDS-polyacrylamide gel electrophoresis, immunoblotting, and mass spectrometry. LPS of both strains were identified as smooth-form LPS with different repeating units. The lipid As were isolated after mild acid hydrolysis and their structures were determined by chemical analysis, by mass spectrometric methods, and by NMR spectroscopy. Both lipid As were characterized by an unusual chemical structure, consisting of a beta-(1-->6)-linked 2,3-diamino-2,3-dideoxy-d-glucopyranose disaccharide carrying six fatty acids that were all hydroxylated. Instead of phosphate groups substituting position O-1 of the reducing and O-4' of the nonreducing end alpha-d-mannopyranose residues were found in these lipid As. Thus, they represent the first lipid As completely missing negatively charged groups. A reduced endotoxic activity as determined by cytokine induction from human macrophages was shown for this novel structure. Only minor differences with respect to fatty acids were detected between the lipid As of the host-dependent wild type strain HD100 and for its host-independent derivative HI100. From the results of the detailed analysis it can be concluded that the wild type strain HD100 synthesizes an innate LPS.  (+info)

Glycolytic and tricarboxylic acid cycle enzyme activities during intraperiplasmic growth of Bdellovibrio bacteriovorus on Escherichia coli. (8/117)

Selected enzyme activities were measured in extracts of the total cell pellets obtained at various times during aerobic intraperiplasmic growth of Bdellovibrio bacteriovorus 109J on anaerobically grown Escherichia coli substrate cells. Initially, the glycolytic enzyme activities were associated with the input of E. coli and the tricarboxylic acid cycle enzyme activities with the input of bdellovibrios. During the first 90 min of Bdellovibrio development, the glycolytic activities declined about 25 to 60%, whereas the tricarboxylic acid cycle activities increased about 10%. Between 110 and 180 min, the glycolytic activities decreased to trace levels and tricarboxylic acid cycle activities increased about 50 to 90%. Both bdellovibrio cell extracts and the cell-free growth menstruum (obtained after bdellovibrio growth on E. coli) caused the inactivation of glycolytic enzymes in E. coli extracts.  (+info)

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