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Marine Ecology Progress Series

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MEPS 144:13-22 (1996)  -  doi:10.3354/meps144013

Marine bacteriophage reproduction under nutrient-limited growth of host bacteria. II. Investigations with phage-host system [H3:H3/1]

Moebus K

When host bacterium H3 is cultivated in artificial seawater at a concentration of 0.6 mg organic nutrients ml-1, its reaction to infection by phage H3/1 changes dramatically with the duration of incubation before phage attack. Cells infected when still in their logarithmic growth phase rapidly produce progeny phage until breakdown of the phage-sensitive population. For cells infected after entering the stationary phase, rate and extent of phage propagation by resting cells decreases for some time, but both parameters rather suddenly increase again for cells infected after prolonged incubation. Phage production may then reach the same level attained by cells infected during logarithmic growth phase; although, with increasing phage concentration, resting cells very effectively become protected from phage attack by pseudolysogeny. This course of events is mainly influenced by the method of incubation of the host (shaken vs still), by the age of the cells before infection, and presumedly by changes in physiological traits of the bacteria when serially subcultured for extended periods of time. The reduction in volume of bacterial culture by repeated withdrawal of aliquots was found to be of minor importance; however, phage production was measurably affected by the transfer of cells to fresh receptacles. With cells which entered their stationary phase up to 36 h before infection, an initial phage concentration of between 10 and 103 PFU (plaque forming units) ml-1 was found to determine the extent, but not the rate, of phage production. The aforementioned observations were also made with cells starved for 3, 8, and 22 additional days before inoculation, except with initial PFU concentrations of 10 and 102 PFU ml-1, when an appreciable increase in phage production was found. In cell suspensions seeded with phage 48 d after set up of the experiment, the highest phage production was found with the lowest initial phage concentration and vice versa. This finding, i.e. the inverse relationship between production and initial concentration, is not in agreement with any of the current hypotheses concerning bacteriophage ecology.

Virus · Phage · Bacteria · Reproduction

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