ABSTRACT
A Gram-stain-negative, aerobic, oxidase-positive, weakly catalase-positive, motile by means of a single polar flagellum, rod-shaped bacterium designated as strain S2-9T was isolated from sediment sampled in Wiyang pond, Republic of Korea. Growth of this strain was observed at 10-40â°C (optimum, 35â°C) and pH 5.5-9.5 (optimum, pH 7.0-8.0) and in the presence of 0-0.5â% NaCl in Reasoner's 2A broth. The major fatty acids (>10â%) of strain S2-9T were C16â:â0 and summed feature 3 (comprising a mixture of C16â:â1 ω7c and/or C16â:â1 ω6c). Ubiquinone-8 was detected as the respiratory quinone. The major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. Strain S2-9T showed the highest 16S rRNA gene sequence similarity to Paucibacter oligotrophus CHU3T (98.7â%), followed by 'Paucibacter aquatile' CR182 (98.4â%), all type strains of Pelomonas species (98.1-98.3â%), Mitsuaria chitosanitabida NBRC 102408T (97.9â%), Kinneretia asaccharophila KIN192T (97.8â%), Mitsuaria chitinivorans HWN-4T (97.4â%), and Paucibacter toxinivorans 2C20T (97.4â%). Phylogenetic trees based on the 16S rRNA gene and whole-genome sequences showed that strain S2-9T formed a tight phylogenetic lineage with Paucibacter species (CHU3T, CR182, and 2C20T). Average nucleotide identity and digital DNA-DNA hybridization values between strain S2-9T and Paucibacter strains were 76.6-79.3% and 19.5-21.5â%, respectively. The genomic DNA G+C content of strain S2-9T was 68.3 mol%. Notably, genes responsible for both sulphur oxidation and reduction and denitrification were found in the genome of strain S2-9T, suggesting that strain S2-9T is involved in the nitrogen and sulphur cycles in pond ecosystems. Based on the polyphasic taxonomic results, strain S2-9T represents a novel species of the genus Paucibacter, for which the name Paucibacter sediminis sp. nov. is proposed. The type strain is S2-9T (=âKACC 22267T=âJCM 34541T).
Subject(s)
Bacterial Typing Techniques , Base Composition , DNA, Bacterial , Fatty Acids , Geologic Sediments , Phylogeny , Ponds , RNA, Ribosomal, 16S , Sequence Analysis, DNA , Ubiquinone , Fatty Acids/analysis , RNA, Ribosomal, 16S/genetics , Geologic Sediments/microbiology , Ponds/microbiology , DNA, Bacterial/genetics , Republic of Korea , Nucleic Acid HybridizationABSTRACT
This study investigated the technical feasibility of using electrogermination to activate dormant cysts as an inoculum for subsequent 14-d photosynthetic astaxanthin production in Haematococcus lacustris. Electrotreatment affected the cell viability, surface charge, and morphology of H. lacustris cysts. At an optimal voltage of 2â¯V for 60â¯min, the cyst germination rate peaked at 44.6â¯% after 1 d, representing a 2.2-fold increase compared with that of the untreated control. Notably, electrogermination significantly enhanced both the astaxanthin content (44.9â¯mg/g cell) and productivity (13.2â¯mg/L/d) after 14 d of photobioreactor cultivation, corresponding to 1.7- and 1.5-fold increases compared with those in control, respectively. However, excessive electrotreatment, particularly at voltages exceeding 2â¯V or for durations beyond 60â¯min, did not enhance the astaxanthin production capability of H. lacustris. Proper optimization of renewable electrogermination can enable sustainable algal biorefinery to produce multiple bioactive products without compromising cell viability and astaxanthin productivity.