Seven closely related xylanolytic, thermophilic bacilli were isolated from mud and water samples from the Gonen and Diyadin hot springs, respectively located in the Turkish provinces of Balikesir and Agri. On the basis of morphology and biochemical characteristics, one of the isolates, designated strain G2T, was studied further. Strain G2T is a xylanolytic, sporulating, Gram-positive, rod-shaped bacterium. The isolate is a thermophilic (optimum temperature for growth, 55–60 °C), facultative anaerobe that grows on a wide range of carbon sources, including glucose, starch, xylose and mannitol. It expressed a high level of xylose isomerase activity on xylose and also on glucose. 16S rRNA gene sequence analysis showed that this isolate resembled Anoxybacillus flavithermus DSM 2641T (>97 % similarity), but 16S–23S rDNA internally transcribed spacer polymorphism PCR showed variation between DSM 2641T and isolate G2T. However, it is also known that analysis of 16S rRNA gene sequences may be insufficient to distinguish between some species. In DNA–DNA hybridization, thermophilic isolate G2T showed relatedness of 53·4 % to A. flavithermus and about 45·0 % to Anoxybacillus pushchinoensis, indicating that it is distinct at the species level. On the basis of the evidence presented, it is proposed that strain G2T (=NCIMB 13933T=NCCB 100040T) be designated as the type strain of Anoxybacillus gonensis sp. nov.

Two thermophilic bacilli were isolated from mud and water samples of the Ayder and Kestanbol hot springs in the provinces of Rize and Canakkale, respectively, in Turkey. Strains AB04^T and K4^T were sporulating, Gram-positive, rod-shaped bacteria. These isolates were moderately thermophilic (with an optimum temperature for growth of 50–55 °C), facultative anaerobes able to grow on a wide range of carbon sources including d-glucose, d-raffinose, d-sucrose, d-xylose, d-fructose, l-arabinose, maltose, d-mannose and d-mannitol. Analysis of the 16S rRNA gene sequences showed that these isolates resembled Anoxybacillus flavithermus DSM 2641^T and Anoxybacillus gonensis NCIMB 13933^T. DNA–DNA hybridization data revealed that thermophilic isolate AB04^T has only 51·2 % relatedness to A. flavithermus, 45·1 % relatedness to Anoxybacillus pushchinoensis and 68·6 % relatedness to A. gonensis. Thermophilic isolate K4^T showed only 60·4 % relatedness to A. flavithermus, 42·9 % relatedness to A. pushchinoensis and 38·5 % relatedness to A. gonensis. On the basis of the DNA–DNA hybridization data, isolates AB04^T and K4^T are not related to A. flavithermus DSM 2641^T, A. pushchinoensis DSM 12423^T or A. gonensis NCIMB 13933^T at the species level, but show relatedness to one another of 40·5 %. On the basis of the data presented, it is proposed that strains AB04^T (=NCIMB 13972^T=NCCB 100050^T) and K4^T (=NCIMB 13971^T=NCCB 100051^T) be designated as the type strains of Anoxybacillus ayderensis sp. nov. and Anoxybacillus kestanbolensis sp. nov., respectively.

The cyclic 3', 5' adenosine monophosphate (cAMP) binding pocket of the cAMP receptor protein (CRP) of Escherichia coli was mutagenized to substitute cysteine or glycine for serine 83; cysteine, glycine, isoleucine, or serine for threonine 127; and threonine or alanine for serine 128. Cells that expressed the binding pocket residue-substituted forms of CRP were characterized by measurements of beta-galactosidase activity. Purified wild-type and mutant CRP preparations were characterized by measurement of cAMP binding activity and by their capacity to support lacP activation in vitro. CRP structure was assessed by measurement of sensitivity to protease and DTNB-mediated subunit crosslinking. The results of this study show that cAMP interactions with serine 83, threonine 127 and serine 128 contribute to CRP activation and have little effect on cAMP binding. Amino acid substitutions that introduce hydrophobic amino acid side chain constituents at either position 127 or 128 decrease CRP discrimination of cAMP and cGMP. Finally, cAMP-induced CRP structural change(s) that occur in or near the CRP hinge region result from cAMP interaction with threonine 127; substitution of threonine 127 by cysteine, glycine, isoleucine, or serine produced forms of CRP that contained, independently of cAMP binding, structural changes similar to those of the wild-type CRP:cAMP complex.