[Adaptation of Anoxybacillus flavithermus ssp. yunnanesis E13(T) to toluene at the level of fatty acid composition of membrane].

OBJECTIVE: Anoxybacillus flavithermus subsp. yunnanensis is now the only species of thermophilic bacteria able to tolerate toxic solvents at high temperature. The adaptive responses of A. flavithermus subsp. yunnanensis E13(T) to toluene on the level of fatty acid composition of membrane were studied in detail. METHODS: The extraction of fatty acids was performed according to the method described in the Sherlock Microbial Identification System manual. The fatty acid compositions were analyzed by gas chromatography mass spectrometry (GC-MS). RESULTS: In presence of 0.3% (V/V) toluene, key moment to adapt the saturated straight-chain fatty acids was that when cells grew from the lag phase to the initial growth phase in liquid. The saturated straight-chain fatty acids were continuously decreased as the strain E13(T) to grow. In survival of the cells in 100% toluene, the saturated straight-chain fatty acids increased significantly. CONCLUSION: A. flavithermus ssp. yunnanesis E13(T) alters its membrane fluidity via fatty acid composition to become more rigid when it is exposed to solvent, which is consistent that commonly found in mesophilic organic solvent-tolerant bacteria. However, it adapted its membrane by increasing straight-chain saturated fatty acids, rather than unsaturated fatty acids, which was demonstrated in mesophilic organic solvent-tolerant bacteria.

A starch-binding domain identified in α-amylase (AmyP) represents a new family of carbohydrate-binding modules that contribute to enzymatic hydrolysis of soluble starch.

A novel starch-binding domain (SBD) that represents a new carbohydrate-binding module family (CBM69) was identified in the α-amylase (AmyP) of the recently established alpha-amylase subfamily GH13_37. The SBD and its homologues come mostly from marine bacteria, and phylogenetic analysis indicates that they are closely related to the CBM20 and CBM48 families. The SBD exhibited a binding preference toward raw rice starch, but the truncated mutant (AmyPΔSBD) still retained similar substrate preference. Kinetic analyses revealed that the SBD plays an important role in soluble starch hydrolysis because different catalytic efficiencies have been observed in AmyP and the AmyPΔSBD.