Nitrogen Fixation Genes in an Endosymbiotic Burkholderia Strain

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Abstract
A novel α-amylase (AmyK38) was found in cultures of an alkaliphilic Bacillus isolate designated KSM-K38. Based on the morphological and physiological characteristics and phylogenetic position as determined by 16S ribosomal DNA gene sequencing and DNA-DNA reassociation analysis, it was suggested that the isolate was a new species of the genus Bacillus. The enzyme had an optimal pH of 8.0 to 9.5 and displayed maximum catalytic activity at 55 to 60°C. The apparent molecular mass was approximately 55 kDa, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the isoelectric point was around pH 4.2. This enzyme efficiently hydrolyzed various carbohydrates to yield maltotriose, maltohexaose, maltoheptaose, and, in addition, maltose as major end products after completion of the reaction. The activity was not prevented at all by EDTA and EGTA at concentrations as high as 100 mM. Moreover, AmyK38 was highly resistant to chemical oxidation and maintained more than 80% of its original activity even after incubation for 1 h in the presence of excess H2O2 (1.8 M).