A Gram-stain-negative, aerobic, non-endospore-forming organism, isolated from the rhizosphere sand of a coastal sand dune plant was studied for its taxonomic position. On the basis of 16S rRNA gene sequence similarity comparisons, strain YU-PRIM-29 was grouped within the genus Halomonas and was most closely related to Halomonas johnsoniae (97.5 %). The 16S rRNA gene sequence similarity to other Halomonas species was <97.5 %. Strain YU-PRIM-29 grew optimally at 28 °C (growth range, 10-36 °C), at a pH of 7-9 (growth range, pH 5.5-12.0) and in the presence of 0.5 to 5 % (w/v) NaCl (growth up to 20 % NaCl). The fatty acid profile from whole-cell hydrolysates supported the allocation of the strain to the genus Halomonas. The fatty acids C18 : 1ω7c and C16 : 0 were found as major compounds, followed by the hydroxylated fatty acid C12 : 0 3-OH. The quinone system consisted predominantly of ubiquinone Q-9. The polar lipid profile was composed of the major lipids diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. In the polyamine pattern, spermidine was the predominant compound. The DNA G+C content was 64.8 mol%. In addition, the results of physiological and biochemical tests also allowed phenotypic differentiation of strain YU-PRIM-29 from its closest-related species. Hence, YU-PRIM-29 represents a new species of the genus Halomonas, for which we propose the name Halomonas malpeensis sp. nov., with YU-PRIM-29 (=LMG 28855=CCM 8737) as the type strain.
In this study, bacteria associated with marine organisms were screened for the production of exopolysaccharides (EPSs) on MY media containing sea salts (2.5%10%). Three selected isolates were identified as Alteromonas sp. PRIM-21, Nitratireductor sp. PRIM-24 and Enterobacter sp. PRIM-26 using 16S rRNA gene sequencing. Optimization of the growth and EPS production kinetics in relation to incubation time were assessed. The purified EPS yield was 590, 650 and 540 mg·L 1 culture media respectively in Alteromonas sp. PRIM-21, Nitratireductor sp. PRIM-24 and Enterobacter sp. PRIM-26. Biochemical and FTIR analyses revealed the presence of biologically important functional groups in the EPS produced by all the three isolates. The EPS produced by Nitratireductor sp. PRIM-24 and Alteromonas sp. PRIM-21 showed 2.0% sulfate content. These bacterial EPS also showed antioxidant and emulsifying activities and the EPS produced by Enterobacter sp.PRIM-26 showed significantly higher antioxidant activities in terms of superoxide (IC 50 0.33 mg·mL 1 ) and DPPH (IC 50 0.44 mg·mL 1 ) radical scavenging. It also showed higher emulsifying activities against selected hydrophobic substrates with EI 24 values above 60%. From the results of the study, it can be concluded that the isolated bacteria produce EPS that can be investigated in detail for biotechnological applications.
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