Cytophaga hutchinsonii is a Gram-negative gliding bacterium which can efficiently degrade crystalline cellulose by an unknown strategy. Genomic analysis suggests the C. hutchinsonii genome lacks homologs to an obvious exoglucanase that previously seemed essential for cellulose degradation. One of the putative endoglucanases, CHU_2103, was successfully expressed in Escherichia coli JM109 and identified as a processive endoglucanase with transglycosylation activity. It could hydrolyze carboxymethyl cellulose (CMC) into cellodextrins and rapidly decrease the viscosity of CMC. When regenerated amorphous cellulose (RAC) was degraded by CHU_2103, the ratio of the soluble to insoluble reducing sugars was 3.72 after 3 h with cellobiose and cellotriose as the main products, indicating that CHU_2103 was a processive endoglucanase. CHU_2103 could degrade cellodextrins of degree of polymerization ≥3. It hydrolyzed p-nitrophenyl β-D-cellodextrins by cutting glucose or cellobiose from the non-reducing end. Meanwhile, some larger-molecular-weight cellodextrins could be detected, indicating it also had transglycosylation activity. Without carbohydrate-binding module (CBM), CHU_2103 could bind to crystalline cellulose and acted processively on it. Site-directed mutation of CHU_2103 demonstrated that the conserved aromatic amino acid W197 in the catalytic domain was essential not only for its processive activity, but also its cellulose binding ability.

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Cytophaga hutchinsonii is an aerobic cellulolytic gliding bacterium. The mechanism of its cell motility over surfaces without flagella and type IV pili is not known. In this study, mariner-based transposon mutagenesis was used to identify a new locus CHU_1797 essential for colony spreading on both hard and soft agar surfaces through gliding. CHU_1797 encodes a putative outer membrane protein of 348 amino acids with unknown function, and proteins which have high sequence similarity to CHU_1797 were widespread in the members of the phylum Bacteroidetes. The disruption of CHU_1797 suppressed spreading toward glucose on an agar surface, but had no significant effect on cellulose degradation for cells already in contact with cellulose. SEM observation showed that the mutant cells also regularly arranged on the surface of cellulose fiber similar with that of the wild type strain. These results indicated that the colony spreading ability on agar surfaces was not required for cellulose degradation by C. hutchinsonii. This was the first study focused on the relationship between cell motility and cellulose degradation of C. hutchinsonii.

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A Gram-stain-negative, aerobic, mesophilic, non-motile bacterium, designated M0104T, was isolated from a gorgonian coral collected from Xieyang island, Guangxi Province, PR China. Colonies of the strain were non-motile cocci and pink. The strain grew at 15–34 °C (optimum, 28 °C), pH 4.5–8.0 (optimum, pH 7.0) and with 0–4% (w/v) NaCl (optimum, 0–2 %). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain M0104T was closely related to Roseomonas deserti JCM 31275T (96.2 %), Roseomonas vastitatis KCTC 62043T (96.0 %), Roseomonas aerofrigidensis JCM 31878T (95.9 %) and Roseomonas oryzae KCTC 42542T (95.7 %). The strain had an assembly size of 5.0 Mb and a G+C content of 71.0mol%. Genes involved in copper, cadmium, lead, arsenic and zinc resistance were identified in the genome of strain M0104T. The digital DNA–DNA hybridization and average nucleotide identity values between the genome sequence of strain M0104T and those of closely related type strains were 19.4–24.9 % and 74.3–81.8 %, respectively. Strain M0104T contained C18:1 ω7c, C18:3 ω3c, anteiso C11:0 and C16:0 as the major fatty acids (>7 %) and ubiquinone Q-10 as the sole isoprenoid quinone. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylcholine were its major polar lipids. Based on its phenotypic, phylogenetic and chemotaxonomic properties, strain M0104T is proposed to represent a novel species within the genus Roseomonas , for which the name Roseomonas coralli sp. nov. is proposed. The type strain is M0104T (=KCTC 62359T=MCCC 1K03632T).