The nucleotide sequence of a 2.7-kilobase segment of DNA containing the sdhA and sdhB genes encoding the flavoprotein (Fp, sdhA) and iron-sulfur protein (Ip, sdhB) subunits of the succinate dehydrogenase of BaciUus subtilis was determined. This sequence extends the previously reported sequence encoding the cytochrome b558 subunit (sdhC) and completes the sequence of the sdh operon, sdhCAB. The The structural genes encoding the subunits of the SDH complex form an operon at 225°on the B. subtilis linkage map (42). For compatibility with Escherichia coli, the B. subtilis genes have been redefined as sdhC (cytb558, formerly sdhA), sdhA (Fp, formerly sdhB), and sdhB (Ip, formerly sdhC), so the operon is transcribed in the order sdhCAB (11,17,23,33,60 (40), and SDHD (32, 60). The nucleotide sequence of the sdh operon (sdhCDAB) of E. coli has been determined previously and compared with that of the frdABCD operon, which encodes the similar but genetically distinct and anaerobically derepressed enzyme fumarate reductase (FRD) (6,7,11,60). The Fp and Ip subunits of the two enzymes exhibit high degrees of mutual sequence homology both for the predicted amino acid sequences and for the corresponding genes. The nucleotide sequence revealed the presence of two hydrophobic subunits encoded by proximal (sdhCD) rather than distal (frdCD) genes, but despite similarities in size and hydropathy profile, there is little homology between the predicted amino acid sequences for the corresponding gene products. The present work is aimed at defining the differences between the 3-and 4-subunit SDH complexes and comparing the analogous complexes of gram-positive and -negative bacteria. Here the nucleotide sequence of the B. subtilis sdhCAB operon is extended by 2.5 kb to include the structural genes encoding the Fp (sdhA) and Ip (sdhB) subunits, and a comparison of the subunit amino acid sequences with those of the analogous subunits of the E. coli SDH and fumarate reductase is presented.
MATERIALS AND METHODSBacteria and plasmids. Plasmid pSH1047 sdhC+ sdhA+ sdhB+ gerE+ has been described elsewhere (17). E. coli MV1OCh3/86 (C600 AtrpES carrying hybrid X prophage Ch3/86 with trfA and trfB of plasmid RK2) was used as a transformation host for preparing plasmid DNA (17). Strain
The difficulty of keeping herds free from Strep. agalactiae for long periods has been demonstrated in five herds. In one sense, however, these herds were not representative of the majority of herds for they were relatively large and under the same management. Furthermore, if one herd became infected with the streptococcus, there was a real risk of the infection spreading to all herds via the hands of the relief milker, particularly if hand stripping was practised and no special precautions were taken by the relief milker.There is no doubt that herds under the same management should take stringent precautions against the spread of infection between herds.
The selective toxicity of the respiratory inhibitor Tinopal AN (1,1‐bis (3,N‐5–dimethylbenzoxazol‐2‐yl) methine p‐toluene sulphonate) towards phytopathogenic bacteria was investigated further and in general was confirmed using more than 160 additional strains of Pseudomonas spp. The mechanism(s) of the resistance shown by saprophytic fluorescent pseudomonads were studied to elucidate the differences between resistant saprophytic and sensitive phytopathogenic Pseudomonas species. Damage to, or partial removal of the cell wall of Tinopal AN‐resistant Pseudomonas aeruginosa, resulted in a marked Tinopal AN‐sensitivity, as judged by the ability of Tinopal AN to inhibit oxygen uptake. Furthermore, removal of part of the lipo‐polysaccharide (LPS) component of the outer membrane also resulted in sensitivity. Mutants of Ps. aeruginosa with modified outer cell walls were tested for their reactions towards Tinopal AN, and two cell wall lipopolysaccharide (LPS) mutants of Escherichia coli (env Al) and Salmonella typhimurium (rfa) were, in contrast to the wild‐type strains, found to be sensitive towards Tinopal AN. The results therefore suggest that the resistance of saprophytic pseudomonads towards Tinopal AN is due (at least in part) to the selectively permeable properties of the outer membrane of the cell wall. The usefulness of Tinopal AN for screening potentially phytopathogenic strains of Pseudomonas was confirmed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.