Cell aggregation and aerobic respiration facilitate survival of Zymomonas mobilis ZM4 in an aerobic minimal medium

Abstract

Zymomonas mobilis produces ethanol from glucose near the theoretical maximum yield, making it a potential alternative to yeast for industrial ethanol production. A potentially useful industrial feature is the ability to form multicellular aggregates called flocs, which can settle 15 quickly and exhibit higher resistance to harmful chemicals. While spontaneous floc-forming Z. mobilis mutants have been described, little is known about the natural conditions that induce Z. mobilis floc formation and the genetic factors involved. Here we found that wild-type Z. mobilis forms flocs in response to aerobic growth conditions but only in a minimal medium. We identified a cellulose synthase gene cluster and a single diguanylate cyclase that are essential 20 for both floc formation and survival in an aerobic minimal medium. We also found that NADH dehydrogenase 2, a key component of the aerobic respiratory chain, is important for survival in an aerobic minimal medium, providing a physiological role for this enzyme which has previously been found to be disadvantageous in aerobic rich media. Supplementation of the minimal medium with vitamins also promoted survival but did not inhibit floc formation. 25

Increased salt tolerance in Zymomonas mobilis strain generated by adaptative evolution

“…These cells constituted a loosened pellet, found as sediment in the fully-grown culture ( Fig. 1), however, we did not observe any floc formation which was shown to be beneficial for stress resistance in Z. mobilis [25]. Based on the cell shapes and the growth profile (Figs.…”

The power of unbiased phenotypic screens – cellulose as a first receptor for the Schitoviridae phage S6 of Erwinia amylovora

“…amylovora (Castiblanco and Sundin, 2018; Römling and Galperin, 2015). Among a variety of exopolysaccharides produced by plant‐associated bacteria, cellulose, with its production stimulated by plant products, has important ecological functions as it, for example, is mediating root attachment of symbionts and plant pathogens to promote infection (Robledo et al ., 2012; Castiblanco and Sundin, 2018; Matthysse, 2018; Jones‐Burrage et al ., 2019; Augimeri and Strap, 2015; Ausmees et al ., 1999; Augimeri et al ., 2015).…”

“…However, genes which regulate cellulose biosynthesis and can substitute the glucan chain such as the bcsEFG gene cluster of the class II cellulose biosynthesis operon of Salmonella typhimurium and Escherichia coli with BcsG as a lipid headgroup phosphotransferase are not encoded by the cellulose biosynthesis gene cluster and flanking genes in E. amylovora (Castiblanco and Sundin, 2018;Römling and Galperin, 2015). Among a variety of exopolysaccharides produced by plant-associated bacteria, cellulose, with its production stimulated by plant products, has important ecological functions as it, for example, is mediating root attachment of symbionts and plant pathogens to promote infection (Robledo et al, 2012;Castiblanco and Sundin, 2018;Matthysse, 2018;Jones-Burrage et al, 2019;Ausmees et al, 1999;.…”