c Two cellulolytic thermophilic bacterial strains, CS-3-2 and CS-4-4, were isolated from decayed cornstalk by the addition of growth-supporting factors to the medium. According to 16S rRNA gene-sequencing results, these strains belonged to the genus Clostridium and showed 98.87% and 98.86% identity with Clostridium stercorarium subsp. leptospartum ATCC 35414 T and Clostridium cellulosi AS 1.1777 T , respectively. The endoglucanase and exoglucanase activities of strain CS-4-4 were approximately 3 to 5 times those of strain CS-3-2, whereas the -glucosidase activity of strain CS-3-2 was 18 times higher than that of strain CS-4-4. The xylanase activity of strain CS-3-2 was 9 times that of strain CS-4-4, whereas the -xylosidase activity of strain CS-4-4 was 27 times that of strain CS-3-2. The enzyme activities in spent cultures following cocultivation of the two strains with cornstalk as the substrate were much greater than those in pure cultures or an artificial mixture of samples, indicating synergism of glycoside hydrolase secretomes between the two strains. Quantitative measurement of the two strains in the cocultivation system indicated that strain CS-3-2 grew robustly during the initial stages, whereas strain CS-4-4 dominated the system in the late-exponential phase. Liquid chromatography-tandem mass spectrometry analysis of protein bands appearing in the native zymograms showed that ORF3880 and ORF3883 from strain CS-4-4 played key roles in the lignocellulose degradation process. Both these open reading frames (ORFs) exhibited endoglucanase and xylanase activities, but ORF3880 showed tighter adhesion to insoluble substrates at 4, 25, and 60°C owing to its five carbohydrate-binding modules (CBMs).
A pale pink and strictly aerobic bacterium, designated strain M71T, was isolated from the soil of a Euphrates poplar forest in Xingjiang, PR China. Cells of the strain were Gram-reaction-negative, rod-shaped and motile by means of a single polar flagellum. Growth occurred at 10–37 °C (optimum 30 °C), at pH 6.0–9.0 (optimum pH 7.0–8.0) and with 0–2.0 % NaCl (w/v, optimum 0 %). Phylogenetic analysis, based on 16S rRNA gene sequences, indicated that strain M71T belongs to the genus Desertibacter in the family Rhodospirillaceae . The 16S rRNA gene sequence of this strain showed 96.2 % sequence similarity with the type strain of Desertibacter roseus 2262T. The respiratory quinone was Q-10 and the predominant cellular fatty acids were C18 : 1ω7c (53.2 %), C16 : 1ω5c (11.0 %), summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c, 10.2 %) and C16 : 0 (8.5 %). The DNA G+C content was 71.2 mol% (HPLC). The strain contained phosphatidylcholine and phosphatidylethanolamine as the predominant polar lipids. On the basis of the phenotypic, chemotaxonomic and phylogenetic data, strain M71T is considered to represent a novel species of the genus Desertibacter , for which the name Desertibacter xinjiangensis sp. nov. is proposed. The type strain is M71T ( = CCTCC AB 209291T = CIP 110127T).
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