Nitrogen regulates chitinase gene expression in a marine bacterium

Abstract

Ammonium concentration and nitrogen source regulate promoter activity and use for the transcription of chiA, the major chitinase gene of Pseudoalteromonas sp. S91 and S91CX, an S91 transposon lacZ fusion mutant. The activity of chiA was quantified by b-galactosidase assay of S91CX cultures containing different ammonium concentrations (NH 4 þ ; 0, 9.5 or 191 mM) and with different nitrogen sources (N-acetylglucosamine (GlcNAc) or glutamate (glt)). S91 chiA expression was found to depend on both the NH 4 þ concentration and source of nitrogen in marine minimal medium (MMM). Pseudoalteromonas sp. S91 and S91CX can use either GlcNAc or glt as a sole source of carbon in MMM containing a standard concentration of 9.5 mM NH 4 þ . Adding excess NH 4 þ , 20 times the standard concentration, to MMM significantly reduced chiA activity below that found in the presence of either GlcNAc or glt. When no NH 4 þ was added to MMM, S91CX was also able to use either GlcNAc or glt as a source of nitrogen; under these conditions chiA activity was significantly increased. Under all conditions tested, GlcNAc induced chiA activity significantly more than glt. Regulation of bacterial chitinases by nitrogen has not been previously reported. Transcriptional start point analysis of S91 chiA, using 5 0 RACE (ligation-anchored PCR), showed that during growth in MMM supplemented with (1) maltose (solely a carbon source for S91), chiA transcription occurred from only one putative r 70 -dependent promoter; (2) the chitin monomer GlcNAc, transcription initiated from two putative r 54 -dependent promoters and (3) glt, transcription initiated from all three putative promoters.

Microdiversity of extracellular enzyme genes among sequenced prokaryotic genomes

“…Extracellular enzymes are commonly produced by prokaryotes in low-nutrient environments to access the resources trapped in high molecular weight compounds (Torriani, 1960;Mü nster and Chrost, 1990;Amon and Benner, 1996;Delpin and Goodman, 2009 et al, 2006) and phosphate acquisition genes varied among strains of Prochlorococcus in relation to the specific nutrient availability where the strains were isolated (Martiny et al, 2006). These patterns of variation were reflected in the distribution of AP-positive genotypes among Cyanobacteria in our data set (Figure 3), and may be the result of frequent local resource adaptation.…”

Nutrient regime regulates complex transcriptional start site usage within a Pseudoalteromonas chitinase gene cluster

“…The presence of potential s 54 -dependent promoters for the expression of chiA, chiB and chiC, indicate a possibility that expression of these chitinase genes could be regulated by nitrogen, as many s 54 -dependent promoters are part of the nitrogen assimilation regulatory system (Zimmer et al, 2000). Delpin and Goodman (2009) describe the work investigating this hypothesis for the regulation of the S91 chiA gene.…”

“…Regulation of bacterial chitinases by nitrogen has not been previously reported. NtrC is a possible candidate as the activator for the s 54 -dependent promoters, as S91 chiA promoter activity appears to be regulated by nitrogen (Delpin and Goodman, 2009). Growth in varying nitrogen concentration and source regulated S91 chiA transcriptional patterns and the collective chiA promoter activity of S91CX (Delpin and Goodman, 2009).…”

Bacterial chitin degradation—mechanisms and ecophysiological strategies

“…In contrast to (GlcNAc) 2 , GlcNAc has also been reported to act as a suppressor of chitinase expression in a Streptomyces strain (Miyashita et al, 2000) and this may be because its main origin in natural systems could be from murein in cell walls rather than chitin (Benner and Kaiser, 2003). Other factors more generally regulating the expression of these and other hydrolytic enzymes are nutrient regime and availability of other, more readily available growth substrates (Techkarnjanaruk et al, 1997; Keyhani and Roseman, 1999; Delpin and Goodman, 2009a,b). The variety of regulating factors are likely to reflect the wide range of ecological niches occupied by chitin degraders.…”