Cell yields and fermentation responses of a Salmonella Typhimurium poultry isolate at different dilution rates in an anaerobic steady state continuous culture

Abstract

The objectives of these studies were to determine cell yield and fermentation responses of a Salmonella enterica serovar Typhimurium poultry isolate using various dilution rates in steady state continuous culture incubations. S. enterica Typhimurium cells were propagated in continuous cultures with a total volume of 0.50 l of Luria Bertani medium containing 0.1% glucose. Dilution rates from 0.0125 to 1.44/h were used. Cell protein concentration generally increased linearly with increased dilution rate up to a rate of 0.54/h and declined at the higher dilution rates. Glucose consumption gave a similar pattern to cell protein concentration by declining at the three highest dilution rates. Short chain fatty acid production was inconsistently influenced by dilution rate. Acetate, the most predominant fatty acid produced, declined at the higher dilution rates, as did propionate. Ammonia production remained stable at the lowest dilution rates, but increased significantly at a dilution rates above 0.27/h.

Emergent Biosynthetic Capacity in Simple Microbial Communities

“…For example, succinate secretion has been demonstrated in B. subtilis [63] and E. coli [64]. Similarly, the primary producers of acetate in our study, S. typhimurium , M. barkeri , and E. coli , are capable of secreting appreciable quantities of this compound under certain conditions [65]–[67]. This analysis further demonstrated that B. subtilis was almost solely responsible for the secretion of several frequent emergent metabolites, including urea, nitrite, glyoxylate, and fumarate, partnering with almost any other species.…”

Immediate Reduction of Salmonella enterica Serotype Typhimurium Viability via Membrane Destabilization following Exposure to Multiple-Hurdle Treatments with Heated, Acidified Organic Acid Salt Solutions

“…RNA was isolated in order to analyze S. Typhimurium gene expression after exposure to SA and SP at pH 4. These two treatments were specifically chosen because (i) acetic and propionic acids are similar in pK a and the corresponding pH 4 organic acid salt treatments have similar ionic strength and salinity (Table 1) and (ii) Salmonella itself produces SA (16) and therefore may have specific mechanisms in place for countering increased SA, possibly contributing to its observed enhanced survival following SA exposure (Fig. 1).…”

Salmonella Pathogenicity and Host Adaptation in Chicken-Associated Serovars

“…Calhoun and Kwon observed substantial enhanced acid tolerance in S. Enteritidis when exposed to 100 mM propionate at neutral pH over a longer period of time (16 h) (329). The enhancement may not be surprising since Salmonella cells cultured under anaerobic growth conditions can produce fermentation acids (330,331), suggesting that some of the resistance to SCFA may be related to protection from their own end products. It is also known that Salmonella can directly catabolize SCFA.…”

“…It appears that even more subtle fluctuations in pH can influence Salmonella growth metabolism. For example, Dunkley et al, using anaerobic continuous cultures, demonstrated that S. Typhimurium glucose-and ATP-based microbial cell yields (calculated as mg of cell protein synthesized per ATP formed or glucose consumed) were decreased when the pH in the growth vessels was shifted from near-neutral pH to levels approaching pH 6.0 (330). Other stress combinations appear to have more of an impact on SCFA inhibition of Salmonella.…”