A Gram-negative, aerobic, motile, rod-shaped, agarolytic bacterium, designated as H7, was isolated from a coastal seawater sample. This strain grows at pH 6.0–8.0, temperature of 15–40 °C, and at an NaCl concentration of 1–7 % (
w/
v).
Ubiquinone-8 was the predominant respiratory quinone, and the DNA G+C content was 45.82 mol%. Analysis of the 16S
rRNA sequence suggests that strain H7 belongs to the genus
Pseudoalteromonas. DNA-DNA hybridization analysis showed DNA relatedness of as low as 55.42 and 40.27 % with its nearest phylogenetic neighbors
Pseudoalteromonas atlantica IAM12927
T and
Pseudoalteromonas espejiana NCIMB2127
T, respectively, which led us to name H7
Pseudoalteromonas hodoensis sp. nov. The type strain is H7
T (=DSM25967
T = KCTC23887
T). An agarase (AgaA7) was purified to homogeneity from the cell-free culture broth of H7 through many steps of chromatography. Purified AgaA7 had an apparent molecular weight of 35 kDa, with a distinct NH
2-terminal sequence of Ala-Asp-Ala-Thr-X-Pro (X, any amino acid) from the reported proteins, implying that it is a novel enzyme. The optimum pH and temperature for agarase activity were 7.0 and 45 °C, respectively. Thin-layer chromatography analysis, mass spectrometry, and enzyme assay using
p-nitrophenyl-α/β-D-galactopyranoside revealed that AgaA7 is both an exo- and endo-type β-agarase that degrades agarose into neoagarotetraose, neoagarohexaose, and neoagarooctaose (minor).
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