Falsibacillus albus sp. nov., isolated from mangrove soil.

A novel Gram-stain-positive, catalase- and oxidase-positive, endospore-forming bacterium, designated GY 10110T, was isolated from mangrove soil collected from Qinzhou, Guangxi province, China. Cells were aerobic, motile with peritrichous flagella and rod-shaped. The strain grew at 15-37 °C (optimum, 28 °C), at 0-3 %(w/v) NaCl (1 %) and at pH 6.0-9.0 (pH 7.0). The major fatty acids of strain GY 10110T were anteiso-C15 : 0, iso-C15 : 0 and iso-C16 : 0. The predominant menaquinone was MK-7. The cell-wall peptidoglycan contained meso-diaminopimelic acid. The polar lipid profile comprised diphosphatidylglycerol, phosphatidylethanolamine, phosphoglycolipid, glycolipid, two unidentified aminophospholipids and three unidentified phospholipids. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain GY 10110T was closely related to Falsibacillus pallidus CCTCC AB 207188T (98.0 % sequence similarity) and Bacillus oceanisediminis CGMCC 1.10115T (96.9 %), respectively. The G+C content of strain GY 10110T based on the whole genome sequence was 42.3 mol%. The novel strain showed an average nucleotide identity (ANI) value of 77.8 % and a digital DNA-DNA hybridization (dDDH) value of 15.6 % with Falsibacillus pallidus CCTCC AB 207188T based on draft genome sequences, followed by Bacillus oceanisediminis CGMCC 1.10115T with ANI and dDDH values of 75.2 and 12.8 %, respectively. The results of the polyphasic taxonomic study, including phenotypic, chemotaxonomic and phylogenetic analysis, showed that strain GY 10110T represents a novel species of the genus Falsibacillus, for which the name Falsibacillus albus sp. nov. is proposed. The type strain is GY 10110T (=CGMCC 1.13648T=NBRC 113502T).

Ottowia flava sp. nov., isolated from fish intestines.

A novel Gram-negative bacterium, non-motile and short rod-shaped, designated strain GY511T, was isolated from the intestines of fish collected from Maowei Sea, China. Growth occurred at pH 6.0-9.0 (optimum 7.0), 4-37 °C (optimum 28 °C) and at 0-2.5% (w/v) NaCl (optimum 1.0%). The result of 16S rRNA gene sequence analysis showed that strain GY511T is closely related to O. oryzae NBRC 113109T (97.6%), O. konkukae DSM 105395T (97.4%), Ottowia beijingensis CGMCC 1.12324T (95.9%), Ottowia pentelensis DSM 21699T (95.2%) and Ottowia thiooxydans DSM 14619T (95.0%). The DNA-DNA hybridization values of strain GY511T with O. oryzae NBRC 113109T and O. konkukae DSM 105395T were 35.4 ± 3.1% and 26.3 ± 1.8%, respectively. The major fatty acids (> 10%) were identified as summed feature 3 (C16:1ω7c and/or C16:1ω6c), C16:0 and summed feature 8 (C18:1ω7c and/or C18:1ω6c) and the major respiratory quinone was ubiquinone-8 (Q-8). The polar lipids comprised diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylmethylethanolamine, two unidentified aminolipids and an unidentified phospholipid. The G+C content of the genomic DNA was 62.9 mol%. Thiosulfate could be utilized as co-substrate for aerobic growth and was oxidised to sulfate. On the basis of phenotypic, chemotaxonomic and molecular data, strain GY511T is considered to represent a novel species of the genus Ottowia, for which the name Ottowia flava sp. nov. is proposed. The type strain is GY511T (= NBRC 113500T = DSM 107425T = CGMCC 1.13650T).

Inhibition of α-amylase Activity by Zn2+: Insights from Spectroscopy and Molecular Dynamics Simulations.

BACKGROUND: Inhibition of α-amylase activity is an important strategy in the treatment of diabetes mellitus. An important treatment for diabetes mellitus is to reduce the digestion of carbohydrates and blood glucose concentrations. Inhibiting the activity of carbohydrate-degrading enzymes such as α-amylase and glucosidase significantly decreases the blood glucose level. Most inhibitors of α-amylase have serious adverse effects, and the α-amylase inactivation mechanisms for the design of safer inhibitors are yet to be revealed. OBJECTIVE: In this study, we focused on the inhibitory effect of Zn2+ on the structure and dynamic characteristics of α-amylase from Anoxybacillus sp. GXS-BL (AGXA), which shares the same catalytic residues and similar structures as human pancreatic and salivary α-amylase (HPA and HSA, respectively). METHODS: Circular dichroism (CD) spectra of the protein (AGXA) in the absence and presence of Zn2+ were recorded on a Chirascan instrument. The content of different secondary structures of AGXA in the absence and presence of Zn2+ was analyzed using the online SELCON3 program. An AGXA amino acid sequence similarity search was performed on the BLAST online server to find the most similar protein sequence to use as a template for homology modeling. The pocket volume measurer (POVME) program 3.0 was applied to calculate the active site pocket shape and volume, and molecular dynamics simulations were performed with the Amber14 software package. RESULTS: According to circular dichroism experiments, upon Zn2+ binding, the protein secondary structure changed obviously, with the α-helix content decreasing and ß-sheet, ß-turn and randomcoil content increasing. The structural model of AGXA showed that His217 was near the active site pocket and that Phe178 was at the outer rim of the pocket. Based on the molecular dynamics trajectories, in the free AGXA model, the dihedral angle of C-CA-CB-CG displayed both acute and planar orientations, which corresponded to the open and closed states of the active site pocket, respectively. In the AGXA-Zn model, the dihedral angle of C-CA-CB-CG only showed the planar orientation. As Zn2+ was introduced, the metal center formed a coordination interaction with H217, a cation-π interaction with W244, a coordination interaction with E242 and a cation-π interaction with F178, which prevented F178 from easily rotating to the open state and inhibited the activity of the enzyme. CONCLUSION: This research may have uncovered a subtle mechanism for inhibiting the activity of α-amylase with transition metal ions, and this finding will help to design more potent and specific inhibitors of α-amylases.