The Survival of Marine Bacteria under Starvation Conditions

The survival under starvation conditions of two selected strains of marine bacteria, a yellow Pseudomonas sp. (strain 95A) and an unidentified oxidative peritrichate Gram negative rod (strain 41), was investigated. The 50% survival times of suspensions in phosphate buffer depended on cell density and were often more than 20 d. A capacity to scavenge atmospheric nitrogenous compounds led to a marked increase in the viability of cell suspensions of 10⁴ cells/ml. Intracellular poly-β-hydroxybutyrate (PHB) prolonged the survival of strain 95A. Strain 41 contained more intracellular protein and this was degraded during starvation in ammonia-free air. Prolonged survival was not explicable in terms of low adenylate charge states. The 'maintenance energy'requirements of strains 95A and 41 in chemostat cultures were 0.042 and 0.04 g glucose/g dry wt/h respectively, compared with dilution-rate-dependent values of 0.051 to 0.856 for Escherichia coli. The low maintenance energy requirements would not alone explain the long viability. Thus no peculiar physiological property such as nitrogen-scavenging, ability to survive at the expense of intracellular PHB or protein, abnormally low cellular protein content, low maintenance energy requirements or a low adenylate charge state fully account for the starvation resistance of these marine bacteria.