The marine bacterium Beneckea natriegens was grown in batch culture on a glucose/ NH,+/salts medium; growth terminated due to either carbon or nitrogen depletion from the medium. Nitrogen-limited cultures converted part of the excess glucose into glycogen whereas the carbon-limited cultures formed little glycogen. Glycogen-rich cultures survived longer than glycogen-poor cultures during starvation. Little protein was utilized during starvation and RNA was degraded as the primary endogenous source of energy. Glycogen was consumed only when the RNA content had decreased to about a third of the growth value.The adenine nucleotide content of nitrogen-limited cultures increased at the start of the stationary phase but the energy charge remained at the growth value of 0.9 to 0.95. The maximum size of the adenine nucleotide pool depended on the concentration of glucose remaining in the medium at the start of the stationary phase but a limiting value of about 60 pmol ATP (g protein)-l was attained, compared with 12 to 14 pmol ATP (g protein)-l in exponentially growing cultures. During extended starvation of both glycogen-rich and glycogen-poor cultures, there was a large decrease in adenine nucleotide content, but the energy charge remained above 0-6 even when viability was very low. I N T R O D U C T I O NThere are many factors that can cause loss of viability of bacteria (Dawes, 1976). During long-term starvation, endogenous metabolites such as non-essential RNA, protein and reserve polymers (glycogen, poly-P-hydroxybutyrate, triacylglycerols and polyphosphate) act as energy sources permitting essential maintenance processes to occur, thereby preserving viability (Dawes & Senior, 1973). Under these circumstances loss of viability may be related to the inability to regenerate ATP due to depletion of endogenous metabolites and reserve polymers. This would be seen as a decrease in the adenine nucleotide content or as a decrease in the ATP : ADP and ATP : AMP ratios, which may be measured as a decrease in energy charge (Atkinson, 1968(Atkinson, , 1978Chapman & Atkinson, 1977;Knowles, 1977Knowles, ,1979.There have been few studies on the adenylate pools of starving bacteria. Chapman et uZ. (1 97 1) showed that, following nitrogen depletion from a glucose-containing growth medium, there was a gradual decrease in the intracellular energy charge of Escherichia cofi strain B from a growth value of about 0-8 to between 0.6 and 0-5 after 60 to 80 h, without loss of viability. The intracellular adenine nucleotide content also decreased during this period. After 60 to 80 h, a rapid decrease in energy charge occurred, coincident with a loss of viability. Montague & Dawes (1974) showed a similar relationship of decrease in energy charge and loss of viability during starvation of Peptococcus pre'votii, which does not form reserve polymers but utilizes RNA as the sole endogenous source of energy. 7 Present address: The College of the Resurrection, Mirfield, West Yorkshire WF14 OBN.

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Cyanide detoxification was studied by immobilisation of fungal mycelia that had been induced to form cyanide hydratase (formamide hydrolyase) which is able to hydrolyse cyanide to formamide. The fungal pathogens of cyanogenic plants, Stemphylium loti, Gloeocercospora sorghi and Fusarium moniliforme were immobilised using polyelectrolyte flocculating agents. The effect of immobilisation on the enzymic properties of S. loti and G. sorghi were investigated. The apparent Km values increased from 21.0 mmol and 25.5 mmol KCN to 43.5 mmol and 71.0 mmol KCN, respectively. The pH profile for the two enzymes widened on immobilisation. The stoichiometry of 1:1 cyanide utilisation to formamide formation was retained on immobilisation, with complete conversion of 70 mmol KCN in 120 min by 0.12 g dry wt of S. loti and in 6 min by 0.13 g dry wt of G. sorghi. When the two fungi were stabilised by immobilisation, and tested in column reactors containing 1.2 g dry wt of S. loti and 1.3 g dry wt of G. sorghi, they completely converted cyanide (70 mmol; added continuously at 7.5 ml h−1) into formamide for 2 days and 30 days, respectively. Stability was enhanced by inclusion of 1.0 mmol glucose in the 70 mmol KCN solution, by a further 10 h for S. loti and an extra 10 days for G. sorghi. Operational stabilities of immobilised G. sorghi (1.3 g dry wt) and F. moniliforme (1.0 g wet wt) in column reactors, with 100 % cyanide conversion, at varying flow rates was investigated. G. sorghi was stable for 15, 10 and 2 days whereas F. moniliforme was only stable for 48, 20 and 10 h at 30, 60 and 120 ml h−1 flow rates respectively.