Effect of Starvation on the Viability and Cellular Constituents of Zymomonas anaerobia and Zymomonas mobilis

Abstract

SUMMARYZymomonas anaerobia and 2. mobilis, grown on glucose + peptone + yeastextract medium, degraded no endocellular carbohydrate, DNA and protein even in prolonged starvation. No significant qualitative changes in protein content during starvation were detected by disc gel electrophoresis of crude extracts. Both organisms had a high content of RNA (22 % w/w) which was degraded on starvation. In 2. anaerobia RNA decreased linearly to 5 % of the dry weight in 125 hr. With 2. mobilis, half the RNA was degraded in the first 24 hr of starvation after which time the decline was much slower. MgC12 (33 mM) prevented RNA breakdown. During growth, the intracellular ATP concentration increased from 0.5 to 1.0 ,ug./mg. dry wt, but began to decrease exponentially in the last generation before growth ceased because of glucose exhaustion. Intracellular ATP content correlated with viability determined by slide culture. The addition of 33 mM-MgC1, to the starvation medium did not affect ATP content, but increased viability. On prolonged starvation (up to 7 days), populations whose viability had fallen to 3 % possessed unimpaired ability to produce ATP from glucose; only after even longer starvation periods was this ability impaired. I N T R O D U C T I O NDuring recent years considerable attention has been focused on the nature of the endogenous metabolism of micro-organisms (for reviews, see Dawes & Ribbons, 1962, 1964 although this work has been confined mainly to aerobic and facultatively anaerobic organisms. By investigating the changes in chemical composition which occur during starvation an insight can be afforded into the substrates utilized in endogenous metabolism and their relation to the viability of the organisms. Anaerobic bacteria, which obtain their energy by substrate-level phosphorylation reactions which are well charted, ought to be particularly amenable to investigation, especially in relation to the problem of 'maintenance energy' (Dawes & Ribbons, 1964 (NCIB 8938) was maintained in a similar manner. This organism grew with a doubling time of about 2 hr, compared with 3.5 hr for 2. anaerobia.Growth of larger quantities of either organism was achieved by transfer of an inoculum from the stock culture to 20 ml. sterile liquid medium. When this culture was gassing vigorously (after about 12 hr) it was used to inoculate one or more litres of medium in round flat-bottomed flasks or aspirators filled to the neck. Zymomonas anaerobia attained stationary phase in 20 hr at 30°, while 2. mobilis took 12 to 15 hr.For starvation experiments organisms were harvested aseptically in closed, sterile centrifuge bottles and the cultures were examined for contamination by phasecontrast microscopic examination of a wet smear.Measurement of bacterial concentration. This was performed turbidimetrically with a Unicam SP 600 spectrophotometer at 570 nm. Extinctions were related to population density by a dry wt calibration curve.Preparation of washed suspensions for starvation experiments. After the appropriate period of growth ...

Kinetics of alcohol production by zymomonas mobilis at high sugar concentrations

“…4, this is associated with lower levels of biomass formation in the Zymomonas fermentation, rather than greater overall rates of ethanol formation and glucose con- Previous kinetic studies with various strains of Z.mobilis have been largely confined to glucose concentrations of less than 10g/l in complex media. (Bauchop and Elsden, 1960;Belaich and Senez, 1965;Forrest,1967;Dawes and Large, 1970;Belaich et al, 1972). …”

ATP Pool and Growth Yield in Selenomonas ruminantium

“…Franzen & Binkley (1961) with E. coli and Smith & Maalare (1964) with Salmonella typhimurium, in batch culture, reported the ATP pool size to be independent of growth rate. Damoglou & Dawes (1967) reported that for E. coli grown in continuous culture the ATP pool remained constant, independent of growth rate, but gave no details, whereas in Zymomonas anaerobia the ATP pool increased during batch growth (Dawes & Large, 1970). Harrison & Maitra (1969) found that the ATP pool size in Klebsiella aerogenes growing in continuous culture limited by glucose, with oxygen in excess, remained constant at growth rates from 0.1 h-l to 0.5 h-l, when the culture was washing out.…”

The Survival of Peptococcus prevotii in Relation to the Adenylate Energy Charge

“…ATP in bacterial extracts was measured by the firefly luminescence method using a high-gain photomultiplier tube as described by Dawes & Large (1970) except that the output of the photomultiplier tube was measured by a Smith ' Servoscribe' linear chart recorder (Smith Industries Ltd, Wembley, Middlesex).…”