Degradation of Cell Constituents by Starved Streptococcus lactis in Relation to Survival

Abstract

SUMMARYStreptococcus lactis organisms were grown in lactose-limited batch culture and transferred, after washing, to phosphate buffer at the growth temperature. Soluble protein was released from viable organisms into the suspending buffer and the intracellular free amino acid pool declined steadily with the components appearing in the suspending buffer; a net increase in the total amount of free amino acid indicated some protein hydrolysis. RNA was hydrolysed, resulting in the release of u.v.-absorbing bases and ribose from the organisms, Conditions which promoted rapid RNA breakdown also produced rapid death rates and long cell division lags in surviving organisms. After 28 hr starvation in buffer containing Mg2+, the bacterial dry wt decreased by 26 %; loss of RNA, protein and free amino acids accounted for 10.3 %, 7-3 % and 2.7 % of the total bacterial mass loss. The products of polymer hydrolysis appeared to be released in an undegraded form into the external buffer and there was no appreciable formation of lactate, ammonia or volatile fatty acids, possibly indicating the absence of any important endogenous energy sources. There was no appreciable degradation of DNA or carbohydrate but phospholipid was broken down on prolonged starvation. No polyglucose or poly-@-hydroxybutyrate was detected in the organisms.

Changes in Constituents and Ultrastructure of Hyphal Compartments during Autolysis of Glucose-starved Penicillium chrysogenum

“…In the latter case the fall in protein, RNA and DNA concentrations halted after 5 hr, whereas in the glucose-starved culture the decline continued, albeit less rapidly. The decrease in electron density and granularity of the groundplasm of starved hyphae is probably indicative of a decrease in ribosome concentration; ribosome concentration in bacteria is directly proportional to growth rate and changes rapidly with changes in growth rate (Tempest & Strange, 1966 Ben-Hamida, 1966) and, as in the present study, the rate of RNA degradation is usually fastest in the early stages of starvation (Postgate & Hunter, 1962;Burleigh & Dawes, 1967;Thomas & Batt, 1969). The ribose derived from RNA degradation is used as an energy source in bacteria (Dawes & Ribbons, 1964).…”

“…The rapid degradation of DNA in starved Penicillium chrysogenum cultures was unexpected, because in bacteria this component is either stable (Mandelstam, I 960 ; Burleigh & Dawes, 1967;Thomas & Batt, 1969) or decreases by only a small amount (Postgate & Hunter, I 962) during starvation ; however, Euglena gracilis, another eucaryotic organism, also degrades its DNA during starvation (Blum & Buetow, 1963). The decrease in the electron density and granularity of the nucleoplasm of 'starved' nuclei of P. chrysogenum is presumably related to the observed loss of DNA, a conclusion which is supported by the fact that they were cytologically very similar to liver nuclei which had been treated with deoxyribonuclease prior to fixation (Georgiev & Chentzov, 1963).…”

“…Membranes thus contain polymers, probably the phospholipids, which are particularly resistant to breakdown. There is only one reported instance of the breakdown of structural lipid during bacterial starvation (Thomas & Batt, 1969). As autolysis proceeded, the hyphae contained fewer and fewer residual membranes (PI.…”

Callianassa trilobata (Crustacea: Thalassinidea) influences abundance of meiofauna and biomass, composition, and physiologic state of microbial communities within its burrow

“…An increase in cyclopropyl acids relative to their precursors occurs as cultures enter stationary phase (Law et al 1963), as pH of the medium decreases (Buist & Findlay 19851, under low oxygen tension, high temperature, and high concentration of magnesium ions (Law 1971). Therefore, cyclopropyl acids apparently form under conditions of physiologic stress, generally when growth has ceased (Thomas & Batt 1969). Indeed, enrichment of cyclopropyl fatty acids has been demonstrated in starved cultures of Vibno cholerae (Guckert et al 1986) and in anaerobically grown enrichment cultures of estuarine sediments (Guckert et al 1985).…”

StarvedPseudomonas syringaecells release strong Cu2+-complexing compounds

“…RNA is extensively degraded, with the release of UV -absorbing materials and free and purine-bound ribose; some species degrade their proteins, with the release of protein fragments, amino-acids and NH4 +; starved bacterial cells generally exhibit decreased levels of amino-acids and release inorganic phosphate; DNA is not a substrate for endogenous metabolism (Mandelstam, 1960;Strange et al, 1961;Dawes and Ribbons, 1962;Postgate and Hunter, 1962;Burleigh and Dawes, 1967;Jacobson and Gillespie, 1968;Sobek et al, 1968;Thomas andBatt, 1969. Boylen andEnsign, 1970;Robertson andBatt, 1973, Boylen andMulks, 1978).…”