The growth of marine Pseudomonas sp. NCIMB 2021 as continuous cultures in the presence of surfaces of AlSl 316 stainless steel allowed the isolation and partial chemical characterization of exopolymers released into the culture medium (free exopolymers), as well as capsular and biofilm exopolymers. Fourier-transform infrared (FTIR) spectroscopy demonstrated the presence of 0-and N-acetylation within the carbohydrate moieties and a predominant 3,,-helical structure of the protein component, highly resistant to hydrogeddeuterium exchange. Differences between the exopolymers were apparent. Relatively less uronic acid residues were detected in the capsular exopolymers compared to either the biofilm or free exopolymers. 0-and Nacetylation were greatest in the biof ilm exopolymer. SDS-PAGE protein profiles confirmed differences between exopolymers. The secondary structures of proteins determined using FTIR spectroscopy indicated that the capsular exopolymer had reduced helical content and an increased aggregated strand content compared to the biofilm exopolymer. However, the free exopolymer had an increased P-sheet component and a reduced unordered component when compared to the biofilm and capsular exopolymers. These data suggest that exopolymer chemistry varies with cellular mode of growth.

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A PCR-based approach combined with microbiological cultivation methods was employed to determine the occurrence of sulfate-reducing bacteria (SRB) in colon biopsy samples from ulcerative colitis patients and from non-colitic controls. The detection of mucosa-associated SRB was carried out by digoxigenin-dUTP-labelled PCR amplification, in liquid Postgate medium B and in a new liquid medium, termed VM medium I. Using Postgate medium B, the growth of SRB was confirmed in 92% of the colitic specimens and in 52% of non-colitic samples. However, PCR analysis and incubation in VM medium I detected SRB in 100% of biopsy material indicating ubiquitous presence of SRB in human colon mucosa.

A novel sulphate-reducing bacterium (Al1 T ) was recovered from a soured oil well in Purdu Bay, Alaska. Light and atomic force microscopy observations revealed that cells were Gram-negative, vibrio-shaped and motile by means of a single polar flagellum. The carbon and energy sources used by the isolate and the salinity, temperature and pH ranges facilitating its growth proved to be typical of a partial lactate-oxidizing, moderately halophilic, mesophilic, sulphate-reducing bacterium. Analysis of the fatty acid profile revealed that C 18 : 0 , isoC 15 : 0 and isoC 17 : 1 v7c were the predominant species. Fatty acid profile and complete 16S rRNA gene sequencing demonstrated the similarity between strain Al1 T and members of the genus Desulfovibrio. The position of strain Al1 T within the phylogenetic tree indicated that it clustered closely with Desulfovibrio vietnamensis DSM 10520 T (98?9 % sequence similarity), a strain recovered from a similar habitat. However, whole-cell protein profiles, Fourier-transform infrared studies and DNA-DNA hybridization demonstrated that, in spite of the high level of 16S rRNA gene sequence similarity, there is sufficient dissimilarity at the DNA sequence level between D. vietnamensis DSM 10520 T and strain Al1 T (10?2 % similarity) to propose that strain Al1 T belongs to a separate species within the genus Desulfovibrio. Based on the results obtained, the name Desulfovibrio alaskensis sp. nov. is therefore proposed, with Al1 T (=NCIMB 13491 T =DSM 16109 T ) as the type strain.

We have developed a complementation assay which allows us to distinguish between mutations affecting subunit assembly and mutations affecting DNA binding in the DNA recognition subunit (HsdS) of the multimeric restriction endonuclease EcoR1241. A number of random point mutations were constructed to test the validity of this assay. Two of the mutants produced were found to be truncated polypeptides that were still capable of complementation with the EcoR1241 Hsd subunits to give an active restriction enzyme of novel DNA specificity. The N-terminal variable domain (responsible for recognition of GAA from the EcoR1241 recognition sequence GAAnnnnnnRTCG) and the spacer region (central conserved region) is intact in both of these mutants. One of these mutant genes (hsdS(delta 50) has been cloned as an active Mtase. Purification of the Mtase proved to be difficult because the complex is weak. However, Mtase activity was obtained from a soluble cell extract, and this allowed us to determine the DNA recognition sequence of the Mtase to be GAAnnnnnnnTTC. This recognition sequence is an inverted repeat of 5'-end of the EcoR1241 recognition sequence. This suggests that the mutant Mtase is assembled from two inverted HsdS(D50) subunits, possibly held together by the HsdM subunits.