ABSTRACT
A novel Gram-stain-negative, facultatively anaerobic and rod-shaped bacterial strain, designated as DAU312T, was isolated from the sea water of the eastern coast of the Republic of Korea. Optimal growth was observed at 25â°C, pH 7.0-8.0 and with NaCl concentrations of 2.0â% (w/v). Catalase and oxidase activities were detected. On the basis of 16S rRNA gene sequences, strain DAU312T showed the highest similarity (99.2â%) to the type strain Shewanella electrodiphila MAR441T. The complete genome sequence of strain DAU312T contains 4â893â483 bp and 40.5âmol% G+C. Phylogenetic analyses based on 16S rRNA gene sequences and the up-to-date bacterial core genes showed that strain DAU312T, S. electrodiphila MAR441T and S. olleyana were all part of the same monophyletic clade. Their average nucleotide identity, digital DNA-DNA hybridization and two-way average amino acid identity values with each other and type strains of close Shewanella species were 83.4-77.5â%, 27.3-22.0â% and 89.8-81.2â%, respectively. The major cellular fatty acids (>10â%) were iso-C15â:â0, summed feature 3 (C16â:â1 ω7Ñ and/or C16â:â1 ω6Ñ) and C16â:â0. Phosphatidylethanolamine and phosphatidylglycerol were the main polar lipids. The respiratory quinones were Q-7, Q-8, MK-7 and MMK-7. Based on these polyphasic taxonomic findings, the name Shewanella goraebulensis sp. nov. is suggested for strain DAU312T, which is considered to represent a novel species of the genus Shewanella. The type strain is DAU312T (=KCTC 72427 T=JCM 35744T=KCCM 43478T).
Subject(s)
Fatty Acids , Seawater , Fatty Acids/chemistry , Phylogeny , RNA, Ribosomal, 16S/genetics , Sequence Analysis, DNA , DNA, Bacterial/genetics , Bacterial Typing Techniques , Base CompositionABSTRACT
Alginate and its derivatives are annually produced approximately 30,000 tons or more and are applied to various industries as they are natural polymers. The global market for alginate and its derivatives has been growing steadily. There is little research compared to other enzymes produced through biomass degradation or modification. An alginate lyase, MtAl138, from Microbulbifer thermotolerans DAU221 was cloned and identified in Escherichia coli BL21 (DE3). MtAl138 contains a highly conserved motif (R538TELR, Q607IH609, and YFKAGVY716NQ), which indicates that it belongs to the polysaccharide lyase family 7 (PL7). MtAl138, with a molecular weight of 77 kDa worked optimally at 45 °C and pH 7.4. MtAl138 showed twice as much activity as when there was no NaCl when there was between 100 and 600 mM NaCl. Moreover, its activity increased in organic solvents such as benzene, hexane, methanol, and toluene. Based on the thin layer chromatography analyses, MtAl38 is an endo-type enzyme that produces di-, tri-, or tetrasaccharides from polyG and polyM. This study provided that MtAl138 is an endoenzyme that showed outstanding enzymatic activity at concentrated salt solutions and organic solvents, which makes it a reasonably attractive enzyme for use in various industries.
