AbstractThe study addresses interaction of bacteria and phages in the host–parasite system in batch and continuous cultures. The study system consists of the auxotrophic strain of Brevibacterium – Brevibacterium sp. 22L – and the bacteriophage of Brevibacterium sp., isolated from the soil by the enrichment method.Closed system. In the investigation of the relationship between the time of bacterial lysis and multiplicity of phage infection it has been found that at a lower phage amount per cell it takes a longer time for the lysis of the culture to become discernible. Another important factor determining cytolysis in liquid medium is the physiological state of bacterial population. Specific growth rate of bacteria at the moment of phage infection has been chosen as an indicator of the physiological state of bacteria. It has been shown that the shortest latent period and the largest output of the phage are observed during the logarithmic growth phase of bacteria grown under favorable nutrient conditions. In the stationary phase, bacterial cells become “a bad host” for the phage, whose reproduction rate decreases, and the lysis either slows down significantly or does not occur at all.Open system. It has been found that in continuous culture, the components of the host–parasite system can coexist over a long period of time. After phage infection, the sizes of the both populations vary for some time and then the density of the host population reaches the level close to that of the uninfected culture. The phage population copies the variations in the density of the host population, but in antiphase. It has been proven that the bacterium becomes resistant to the phage rather soon. It has been supposed that primary resistance is of physiological origin, because the percentage of cells that have survived lysis – about 0.2% of the initial bacterial population – is too high for phage-resistant mutants. Bacteria and phages cultured over extended periods of time in the host–parasite system have been found to co-evolve. The stressful effect of the phage causes development of bacteria resistant to this phage, then a mutant phage capable of lysing these bacteria evolves, etc.
Host–parasite interactions in closed and open microbial cultivation system
Advances in Space Research ; 41 , 5 ; 773-776
2007-03-25
4 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
Host–parasite interactions in closed and open microbial cultivation system
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