Recent Research Progress in the Applied Microbiology Laboratory : Enzymes, Toxins and Cell-Envelope Structure of Environmental and Pathogenic Bacteria(Recent Topics of the Agricultunal Biological Science in Tohoku University)

Here we describe the current status of our studies of xylanases of Paenibacillus sp. W-61, poly (D-lactic acid) hydrolases of Amycolatopsis sp. K104-1 and Brevibacterium sp. 93, pectin lyase of plant pathogenic Pectobacterium carotovora and bi-component toxins of Staphylococcus aureus. Paenibacillus sp. W-61 utilizes xylan as a carbon source via three enzymes, of which Xyn5 plays a crucial role both in xylan utilization and in the synthesis of the other two xylanases. Understanding the roles of each xylanase in xylan degradation will help to develop an enzymatic preparation of xylose from xylan. The poly (D-lactic acid) [PLA] hydrolases of Amycolatopsis sp. K104-1 and Brevibacterium sp. 93 appear to be novel enzymes with potential for PLA recycling. We recently purified and characterized the PLA hydrolases produced by these bacteria. The plant-soft rotting bacterium P. carotovora produces pectin lyase, a potential pathogenic factor, and a bacteriocin when exposed to DNA-damaging agents. We recently determined the cis-acting regulatory sequences responsible for the DNA-damage-inducible synthesis of the enzyme and bacteriocin. Leukocidin and γ-hemolysin are bi-component toxins that lyse leukocytes and erythrocytes respectively. We describe the molecular structure and pore-forming mechanism of the toxin components encoded by the chromosome and by a phage genome. Finally, we briefly describe the cell-envelope structure of the rumen bacterium Selenomonas ruminantium and its outer membrane protein Mep45 that possibly bridges the outer membrane and the peptidoglycan. The objects of our studies include environmental bacteria (xylanolytic Paenibacillus sp. W-61 and poly (D-lactic acid)-hydrolyzing bacteria Amycolatopsis sp. K104-1 and Brevibacterium sp. 93), as well as the plant and animal pathogens, Pectobacterium carotovora and Staphylococcus aureus, respectively. Here we briefly describe the current status of our investigations into these bacteria, their extracellular enzymes (or toxins), and an outer membrane protein in the rumen bacterium Selenomonas ruminantium subsp. lactilytica. Our research also includes polyglutamate biosynthesis and the degradation enzymes of a Bacillus subtilis Natto starter, acetan (a polysaccharide produced by Acetobacter and Gluconobacter)-degrading enzymes of Paenibacillus sp. and catabolic enzymes of amino acid and polyamine in Pseudomonas aeruginosa PAOl. The topics of these projects are available on our Web site