Bdellovibrio bacteriovorus gen. et sp. n., a predatory, ectoparasitic, and bacteriolytic microorganism
- 840 Downloads
Bdellovibrio bacteriovorus, gen. et sp. n., a predatory and ectoparasitic microorganism with lytic activity against susceptible bacteria, is described, as are techniques for isolation and cultivation. These unusual bacteria cause reactions that are similar in their outward manifestations to bacteriophage-induced lysis. Upon plating a mixture of host bacteria and parasites, confluent lysis or single plaque formation occurs, just as in titration experiments with bacteriophage. However, the parasite plaques develop more slowly than phage plaques. Lysis of host bacteria in liquid culture is accompanied by a decrease in optical density; actually, a population of infected host bacteria is replaced by a population of the tiny parasite.
Individual cells of the presently known strains ofBdellovibrio bacteriovorus are typically about 0.3 µ in width and, thus, are considerably narrower than ordinary bacteria. Therefore, they can pass Millipore filters of 0.45 µ pore size diameter. Their shape is often vibrio-like. They possess one unusually thick polar flagellum of about 50 mµ diameter, and they show a distinctive type of motility.
The interaction betweenBdellovibrio and the attacked host bacterium can be followed in the phase-contrast microscope; it is characterized by a physical attack of the highly motile parasite, attachment to the bacterial cell surface, and lysis of the host cell.
It has not yet been possible to cultivateBdellovibrio in its parasitic form on any artificial substrate. All parasitic strains require living host cells for their propagation. However, saprophytic mutants can be selected from a population of the parasite. These saprophytic derivatives are unable to lyse living bacteria as does the wild-type parasite. On the basis of morphological and physiological properties, a saprophyte strain which has been examined in some detail shows no close relationship to any of the already known categories of bacteria.
A study of the kinetics of growth ofBdellovibrio in mixed culture with a susceptible host has disclosed that the number of parasites produced is not proportional to the number of host bacteria killed during the same period. After the majority of the host cells has been destroyed, there is still a considerable increase in parasites, indicating that they grow at the expense of material released from the lysed bacteria. Under the conditions of this trial, the generation time is about 100 minutes.
All presently known isolates ofBdellovibrio possess lytic activity only against gram-negative bacteria. The individual strains, however, show certain differences in their host activity spectra; some have a restricted host range, while others are able to attack a broad spectrum of host bacteria.
KeywordsLytic Activity Host Bacterium Parasitic Strain Bacterial Cell Surface Polar Flagellum
Unable to display preview. Download preview PDF.
- Houwink, A. L. 1951.Caulobacter versusBacillus spec. div. Nature168 654–655.Google Scholar
- Masudo, S. 1957. Studies on theCaulobacter in Japan. J. Japanese Botany32 321–331.Google Scholar
- Norén, B. 1953. Studies on myxobacteria. Il. Bacteriolytic activity. Svensk Botan. Tidskr.47 309:332.Google Scholar
- Norén, B. 1955. Studies on myxobacteria. IV. Lytic activity on different eubacteria. Svensk Botan. Tidskr.49 282–294.Google Scholar
- Norén, B. 1960. Notes on the bacteriolytic activity ofMyxococcus virescens. Svensk Botan. Tidskr.54 550–560.Google Scholar
- Stolp, H. 1961. Neue Erkenntnisse über phytopathogene Bakterien und die von ihnen verursachten Krankheiten. I. Verwandschaftsbeziehungen zwischen phytopathogenenPseudomonas-“Arten” und saprophytischen Fluoreszenten auf der Grundlage von Phagenreaktionen. Phytopathol. Z.42 197–262.Google Scholar
- Stolp, H. undPetzold, H. 1962. Untersuchungen über einen obligat parasitischen Mikro-organismus mit lytischer Aktivität fürPseudomonas-Bakterien. Phytopathol. Z.45 364–390.Google Scholar
- Stolp, H. andStarr, M. P. 1963. A parasite with lytic activity against pseudomonads. Bacteriol. Proc.1963 47.Google Scholar
- Stove, J. L. 1963. The biology ofCaulobacter. Ph. D. Thesis, University of California, Berkeley.Google Scholar
- Stove, J. L. andStanier, R. Y. 1962. Cellular differentiation in stalked bacteria. Nature196 1189–1192.Google Scholar