The Role of Proline in Osmoregulation in Salmonella Typhimurium and Escherichia Coli

Mesophilic Aeromonas UDP-glucose pyrophosphorylase (GalU) mutants show two types of lipopolysaccharide structures and reduced virulence

“…Besides its function as a substrate for glucosyltransferases resulting in glucosylated surface structures, UDP-glucose plays a well-established biochemical role as a glycosyl donor in the enzymic biosynthesis of carbohydrates. Some examples in Gramnegative bacteria are synthesis of the osmoprotectants trehalose (under conditions of high osmolarity) and membrane-derived oligosaccharide (under conditions of low osmolarity) in E. coli (Csonka & Epstein, 1996); synthesis of UDP-4-amino-4-deoxy-L-arabinose, which is incorporated into lipid A of Salmonella enterica serovar Typhimurium to protect against antimicrobial cationic peptides, especially polymyxin B (Ernst et al, 1999); and synthesis of UDP-galactose, which serves as a donor for several surface structures, including glycosylated pili in Neisseria meningitidis (Stimson et al, 1995). It is less clear whether UDP-glucose additionally acts as an intracellular signal molecule.…”

“…GalU is a UDP-glucose pyrophosphorylase responsible for synthesis of UDP-glucose from glucose 1-phosphate and UTP. Besides its function as a substrate for glucosyltransferases resulting in glucosylated surface structures, UDP-glucose plays a well-established biochemical role as a glycosyl donor in the enzymic biosynthesis of carbohydrates (Csonka & Epstein, 1996;Stimson et al, 1995). The galU gene was found to be important for pathogenesis of infections due to a number of Gram-negative pathogens, including Actinobacillus pleuropneumoniae (Rioux et al, 1999), Escherichia coli (Komeda et al, 1977), Klebsiella pneumoniae (Chang et al, 1996), Pseudomonas aeruginosa (Evans et al, 2002;Priebe et al, 2004), Shigella flexneri (Sandlin et al, 1995) and Vibrio cholerae (Nesper et al, 2001).…”

Osmoregulation of the opuE proline transport gene from Bacillus subtilis: contributions of the sigma A‐ and sigma B‐dependent stress‐responsive promoters

“…Consistent with this conclusion, high concentrations of the membranepermeable glycerol fail to induce OpuE-mediated proline uptake in contrast to ionic or non-ionic compounds capable of establishing osmotically effective concentration gradients across the cytoplasmic membrane (von Blohn et al, 1997). Thus, osmotic control of opuE P-1 activity rather depends on consequences of the rise in the environmental osmolarity, such as the drop in turgor, uptake of K þ , changes in the ionic and physical composition of the cytoplasm, or alterations in the supercoiling of the chromosomal DNA (Sutherland et al, 1986;Higgins et al, 1988;Dattananda et al, 1991;Csonka and Epstein, 1996;Conter et al, 1997). The independence of the osmoregulation of the A -dependent opuE P-1 promoter from the B regulon implies that at least two different signal transduction pathways operate in B. subtilis to communicate osmotic changes in the environment to the transcription apparatus of the cell.…”

“…In addition to their major contribution to the osmotic balance, compatible solutes are thought to serve as stabilizers of enzymes and cell components against the deleterious effects of high ionic strength (Galinski and Trü per, 1994;Yancey, 1994). The intracellular amassing of compatible solutes is not restricted to the prokaryotic world (Galinski and Trüper, 1994;Csonka and Epstein, 1996) but is also widely used as response to osmo-stress in fungal, plant, animal and even human cells (Rhodes andHanson, 1993, Blomberg, 1997;Burg et al, 1997).…”

Growth Enhancement of the Halotolerant Brevibacterium sp. JCM 6894 by Methionine Externally Added to a Chemically Defined Medium

“…In general, microbial growth under salt stress is closely related to the accumulation of organic solutes, such as glycine betaine, proline, ectoine, trehalose, etc., in the cytoplasm to cope with osmotic stress Csonka and Epstein, 1996 . Except for the organic solutes, K + acts as an osmoprotectant.…”