Halosquirtibacter laminarini gen. nov., sp. nov. and Halosquirtibacter xylanolyticus sp. nov., marine anaerobic laminarin and xylan degraders in the phylum Bacteroidota

The bacterial group of the phylum Bacteroidota greatly contributes to the global carbon cycle in marine ecosystems through its specialized ability to degrade marine polysaccharides. In this study, it is proposed that two novel facultative anaerobic strains, DS1-an-13321T and DS1-an-2312T, which were isolated from a sea squirt, represent a novel genus, Halosquirtibacter, with two novel species in the family Prolixibacteraceae. The 16S rRNA sequence similarities of these two strains were 91.26% and 91.37%, respectively, against Puteibacter caeruleilacunae JC036T, which is the closest recognized neighbor. The complete genomes of strains DS1-an-13321T and DS1-an-2312T each consisted of a single circular chromosome with a size of 4.47 and 5.19 Mb, respectively. The average amino acid identity and the percentage of conserved proteins against the type species of the genera in the family Prolixibacteraceae ranged from 48.33 to 52.35% and 28.34-37.37%, respectively, which are lower than the threshold for genus demarcation. Strains DS1-an-13321T and DS1-an-2312T could grow on galactose, glucose, maltose, lactose, sucrose, laminarin, and starch, and only DS1-an-2312T could grow on xylose and xylan under fermentation conditions. These strains produced acetic acid and propionic acid as the major fermentation products. Genome mining of the genomes of the two strains revealed 27 and 34 polysaccharide utilization loci, which included 155 and 249 carbohydrate-active enzymes (CAZymes), covering 57 and 65 CAZymes families, respectively. The laminarin-degrading enzymes in both strains were cell-associated, and showed exo-hydrolytic activity releasing glucose as a major product. The xylan-degrading enzymes of strain DS1-an-2312T was also cell-associated, and had endo-hydrolytic activities, releasing xylotriose and xylotetraose as major products. The evidence from phenotypic, biochemical, chemotaxonomic, and genomic characteristics supported the proposal of a novel genus with two novel species in the family Prolixibacteraceae, for which the names Halosquirtibacter laminarini gen. nov., sp. nov. and Halosquirtibacter xylanolyticus sp. nov. are proposed. The type strain of Halosquirtibacter laminarini is DS1-an-13321T (= KCTC 25031T = DSM 115329T) and the type strain of Halosquirtibacter xylanolyticus is DS1-an-2312T (= KCTC 25032T = DSM 115328T).

Gaoshiqia sediminis gen. nov., sp. nov., isolated from coastal sediment

A Gram-stain-negative, facultative anaerobic, motile, rod-shaped and orange bacterium, designated A06^T, was obtained off the coast of Weihai, PR China. Cells were 0.4-0.5×0.6-1.0 µm in size. Strain A06^T grew at 20-40 °C (optimum, 33 °C), at pH 6.0-8.0 (optimum, pH 6.5-7.0) and in the presence of 0-8 % NaCl (w/v) (optimum, 2 %). Cells were oxidase and catalase positive. Menaquinone-7 was detected as the major respiratory quinone. The dominant cellular fatty acids were identified as C_15:0 2-OH, iso-C_15:0, anteiso-C_15:0 and iso-C_15:1  ω6c. The DNA G+C content of strain A06^T was 46.1 mol%. The polar lipids were phosphatidylethanolamine, one aminolipid, one glycolipid and three unidentified lipids. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain A06^T is a member of the family Prolixibacteraceae and exhibited the highest sequence similarity to Mangrovibacterium diazotrophicum DSM 27148^T (94.3 %). Based on its phylogenetic and phenotypic characteristics, strain A06^T is considered to represent a novel genus in the family Prolixibacteraceae, for which the name Gaoshiqia gen. nov. is proposed. The type species is Gaoshiqia sediminis sp. nov., with type strain A06^T (=KCTC 92029^T=MCCC 1H00491^T). The identification and acquisition of microbial species and genes in sediments will help broaden the understanding of microbial resources and lay a foundation for its application in biotechnology. Strain A06^T uses an enrichment method, so the isolation of strain A06^T is of great significance to the enrichment of marine microbial resources.

Long-term effectiveness of bioaugmentation with rumen culture in continuous anaerobic digestion of food and vegetable wastes under feed composition fluctuations

Biogas plants treating food waste (FW) often experience feed load and composition fluctuations. In Korea, vegetable waste from the preparation of kimchi comprises over 20% of the total FW production during the Kimjang season. The large production of Kimjang waste (KW) can cause mechanical and operational problems in FW digesters. This study investigated the long-term effectiveness of bioaugmentation with rumen culture (38 months) in an anaerobic reactor co-digesting FW with varying amounts of KW. The bioaugmented reactor maintained better and stabler performance under recurrent fluctuations in feed characteristics than a non-bioaugmented control reactor, particularly under high ammonia conditions. Bioaugmentation increased microbial diversity, thereby improving the resilience of the microbial community. Some augmented microorganisms, especially Methanosarcina, likely played an important role in it. The results suggest that the proposed bioaugmentation strategy may provide a means to effectively treat and valorize KW-and potentially other seasonal lignocellulosic wastes-by co-digestion with FW.