Contribution of phosphoglucosamine mutase to determination of bacterial cell morphology in Streptococcus gordonii

Chitin degradation potential and whole-genome sequence of Streptomyces diastaticus strain CS1801

The aim of this study was to evaluate the chitin degradation potential and whole-genome sequence of Streptomyces diastaticus strain CS1801, which had been screened out in our previous work. The results of fermentation revealed that CS1801 can convert the chitin derived from crab shells, colloidal chitin and N-acetylglucosamine to chitooligosaccharide. Additional genome-wide analysis of CS1801 was also performed to explore the genomic basis for chitin degradation. The results showed that CS1801 possesses a chromosome with 5,611,479 bp (73% GC) and a plasmid with 1,388,284 bp (73% GC). The CS1801 genome consists of 7584 protein-coding genes, 90 tRNA and 21 rRNA operons. In addition, the results of genomic CAZyme analysis indicated that CS1801 comprises 103 glycoside hydrolase family genes, which could regulate the glycoside hydrolases that contribute to chitin degradation. The whole-genome information of CS1801 could highlight the mechanism underlying the chitin degradation activity of CS1801, strongly indicating that CS1801 is characterized by a substantial number of genes encoding chitinases and the complete metabolic pathway of chitin, conferring CS1801 with promising potential applicability in chitooligosaccharide production.

Comparative transcriptional profiling of tildipirosin-resistant and sensitive Haemophilus parasuis

Numerous studies have been conducted to examine the molecular mechanism of Haemophilus parasuis resistance to antibiotic, but rarely to tildipirosin. In the current study, transcriptional profiling was applied to analyse the variation in gene expression of JS0135 and tildipirosin-resistant JS32. The growth curves showed that JS32 had a higher growth rate but fewer bacteria than JS0135. The cell membranes of JS32 and a resistant clinical isolate (HB32) were observed to be smoother than those of JS0135. From the comparative gene expression profile 349 up- and 113 downregulated genes were observed, covering 37 GO and 63 KEGG pathways which are involved in biological processes (11), cellular components (17), molecular function (9), cellular processes (1), environmental information processing (4), genetic information processing (9) and metabolism (49) affected in JS32. In addition, the relative overexpression of genes of the metabolism pathway (HAPS_RS09315, HAPS_RS09320), ribosomes (HAPS_RS07815) and ABC transporters (HAPS_RS10945) was detected, particularly the metabolism pathway, and verified with RT-qPCR. Collectively, the gene expression profile in connection with tildipirosin resistance factors revealed unique and highly resistant determinants of H. parasuis to macrolides that warrant further attention due to the significant threat of bacterial resistance.

Biology, Mechanism, and Structure of Enzymes in the α-d-Phosphohexomutase Superfamily

Enzymes in the α-d-phosphohexomutases superfamily catalyze the reversible conversion of phosphosugars, such as glucose 1-phosphate and glucose 6-phosphate. These reactions are fundamental to primary metabolism across the kingdoms of life and are required for a myriad of cellular processes, ranging from exopolysaccharide production to protein glycosylation. The subject of extensive mechanistic characterization during the latter half of the 20th century, these enzymes have recently benefitted from biophysical characterization, including X-ray crystallography, NMR, and hydrogen-deuterium exchange studies. This work has provided new insights into the unique catalytic mechanism of the superfamily, shed light on the molecular determinants of ligand recognition, and revealed the evolutionary conservation of conformational flexibility. Novel associations with inherited metabolic disease and the pathogenesis of bacterial infections have emerged, spurring renewed interest in the long-appreciated functional roles of these enzymes.