Bacteriovorax

Bacteriovorax is a genus containing a single species of bacterium in the family Bacteriovoracaceae, Bacteriovorax stolpii. It is a predator that feeds on larger Gram-negative bacteria.[2] These prey bacteria tend to live in enteric environments and have similar lipopolysaccharide structures.[3] Bacteriovorax stolpii recognizes its prey by outer membrane protein receptors, which explains why Gram-positive bacteria that lack outer membranes do not serve as prey.[3] They prey on bacteria by invading the interperiplasmic space where they feed, grow, and reproduce.[3] Bacteriovorax stolpii used to be classified in the genus Bdellovibrio because of similar morphologies and lifestyle characteristics, however they were recognized as a new genus through phylogenetic analysis.[4]

Bacteriovorax
Scientific classification
Domain:
Bacteria
Phylum:
Proteobacteria
Class:
Deltaproteobacteria
Order:
Bdellovibrionales
Family:
Bacteriovoracaceae
Genus:
Bacteriovorax
Species:
B. stolpii
Binomial name
Bacteriovorax stolpii
(Seidler et al. 1972) Baer et al. 2000[1]
Synonyms
  • Bdellovibrio stolpii Seidler et al.
  • Bacteriolyticum stolpii Piñeiro et al. 2008

Characteristics

The genera Bacteriovorax and Bdellovibrio share numerous morphological and lifestyle characteristics.[3] Bacteriovorax and similar genera are recognized by their presence of sphingolipids, which are not widely distributed in prokaryotes.[2] Bacteriovorax stolpii is known for the presence of sphinophosphonolipids in its membranes.[2] The genome size of the genus Bacteriovorax has been noted from 2.0–2.6 Mb.[3] Bacteriovorax is only predatory to Gram-negative bacteria, though they have been found in the gut of humans.[3] Bacteriovorax and Bdellovibrio are approximately 0.2-0.4 x 0.5-1.4 μm, are aerobic, with oxygen as a terminal electron acceptor, and are mesophilic.[3] They display a typical Gram-negative morphology and are motile by a single, polar, sheathed flagellum.[3]

History

The description of Bacteriovorax stolpii is based on the original description by Seidler et al.[5] Strain Uki2T is the only isolate described at this time and is the type strain of Bacteriovorax stolpii.[4] This isolate has a GC content of 41±8 mol%.[5] The optimal temperature range for growth of this organism is 15–35 °C. The major cellular fatty acids are 5:1ω8c13:0 and 13:0iso.[6] Uki2T is sensitive to most antibiotics tested (penicillin, streptomycin, neomycin, kanamycin, gentamicin, methicillin, nalidixic acid, pteridine 0/129 and vancomycin).[6]

Life cycle

Members of the Bacteriovorax exhibit the same general morphological and life cycle features as described for the genus Bdellovibrio.[3] In addition, members of this genus exhibit a biphasic life cycle, with the potential of displaying an actively predacious form as well as a PI (predatory independent), saprophytic form capable of growing on nutrient medium. Prey-dependent (wild-type) strains are comma-shaped rods, 0±5–1±4 µm in length, which demonstrate a predatory lifestyle in the presence of susceptible prey bacteria. The wild-type strains are motile by a single, polar flagellum. PI cells (mutants) are pleomorphic, demonstrating a range of cell shapes from simple rods to long, tightly spiral shaped cells.[4]

Reclassification

Most bacteria that prey on Gram-negative bacteria were lumped together in the genus Bdellovibrio.[4] This was done regardless of their isolation from various habitats and unstudied phylogenetic relatedness.[4] The previously wide genus included differences in sodium chloride tolerance and %G+C content.[3] Bacteriovorax stolpii and Bacteriovorax starrii were compared to Bdellovibrio bacteriovorus, the model bacterium for its genus, using 16S rDNA sequences and analyses.[4] There was only 81.7% 16S rDNA sequence similarity between Bdellovibrio bacteriovorus and Bacteriovorax stolpii.[3] DNA-DNA hybridization also only yielded <4% hybridization between the species.[4] On these findings, the genus Bacteriovorax was created and Bacteriovorax stolpii and Bacteriovorax starrii moved into it.[4] In 2015, Bacteriovorax marinus and Bacteriovorax litoralis were reclassified as Halobacteriovorax, leaving B. stolpii as the only species in the genus.[7]

References
  1. Parte, A.C. "Bacteriovorax". www.bacterio.net.
  2. Jayasimhulu, K.; Hunt, S.M.; Kaneshiro, E.S.; Watanabe, Y.; Giner, J-L. (2007). "Detection and Identification of Bacteriovorax stolpii UKi2 Sphingophosphonolipid Molecular Species". Journal of the American Society for Mass Spectrometry. 18 (3): 394–403. doi:10.1016/j.jasms.2006.10.014. PMID 17123828.
  3. Bergey, D.H.; Brenner, D.J.; Krieg, N.R.; Staley, J.T. (2005). Bergey's Manual of Systematic Bacteriology. Volume 2. The Proteobacteria. Part C. The Alpha-, Beta-, Delta-, and Epsilonproteobacteria. New York, NY: Springer. pp. 1053–7.
  4. Baer, Marcie L.; Jacques Ravel & Jongsik Chun (2000). "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". International Journal of Systematic and Evolutionary Microbiology. 50 (1): 219–24. doi:10.1099/00207713-50-1-219. PMID 10826807.
  5. Althauser, M.; Samsonoff, W. A.; Anderson, C. & Conti, S. F. (1972). "Isolation and preliminary characterization of bacteriophages for Bdellovibrio bacteriovorus". J Virol. 10 (3): 516–23. PMC 356493. PMID 4116140.
  6. Guether, D. L., Osterhout, G. J., Dick, J. D. & Williams, H. N. (1993). Analysis of fatty acid composition of Bdellovibrio isolates. Abstract Q-243 presented at the 93rd General Meeting of the American Society for Microbiology, Atlanta, Georgia, USA.
  7. Koval, S. F.; Williams, H. N.; Stine, O. C. (2015). "Reclassification of Bacteriovorax marinus as Halobacteriovorax marinus gen. nov., comb. Nov. And Bacteriovorax litoralis as Halobacteriovorax litoralis comb. Nov.; description of Halobacteriovoraceae fam. Nov. In the class Deltaproteobacteria". International Journal of Systematic and Evolutionary Microbiology. 65 (Pt 2): 593–597. doi:10.1099/ijs.0.070201-0. PMC 4811658. PMID 25406234.
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