Restriction-Modification Systems

In the following pages, I consider three directions one might head in in capturing adjectival hydras. Facts considered here suggest that adjectival hydras are indeed more similar to RelC hydras than they are to RNR and other constructions with shared material. Yet extending existing accounts of traditional hydras to the adjectival construction is not without its challenges. In this squib, I call attention to some of these, but leave the ultimate analysis still open.

Campylobacter jejuni is the leading cause of bacterial foodborne diarrhoeal disease worldwide. Despite the microaerophilic nature of the bacterium, C. jejuni can survive the atmospheric oxygen conditions in the environment. Bacteria that can survive either within a host or in the environment like C. jejuni require variable responses to survive the stresses associated with exposure to different levels of reactive oxygen species. The MarR-type transcriptional regulators RrpA and RrpB have recently been shown to play a role in controlling both the C. jejuni oxidative and aerobic stress responses. Analysis of 3,746 C. jejuni and 486 C. coli genome sequences showed that whilst rrpA is present in over 99% of C. jejuni strains, the presence of rrpB is restricted and appears to correlate with specific MLST clonal complexes (predominantly ST-21 and ST-61). C. coli strains in contrast lack both rrpA and rrpB. In C. jejuni rrpB + strains, the rrpB gene is located within a variable genomic region containing the IF subtype of the type I Restriction-Modification (hsd) system, whilst this variable genomic region in C. jejuni rrpB − strains contains the IAB subtype hsd system and not the rrpB gene. C. jejuni rrpB − strains exhibit greater resistance to peroxide and aerobic stress than C. jejuni rrpB + strains. Inactivation of rrpA resulted in increased sensitivity to peroxide stress in rrpB + strains, but not in rrpB − strains. Mutation of rrpA resulted in reduced killing of Galleria mellonella larvae and enhanced biofilm formation independent of rrpB status. The oxidative and aerobic stress responses of rrpB − and rrpB + strains suggest adaptation of C. jejuni within different hosts and niches that can be linked to specific MLST clonal complexes.

BssHII restriction endonuclease cleaves 54-GCGCGC-34 on double-stranded DNA between the first and second bases to generate a four base 54 overhang. BssHII restriction endonuclease was purified from the native Bacillus stearothermophilus H3 cells and its N-terminal amino acid sequence was determined. Degenerate PCR primers were used to amplify the first 20 codons of the BssHII restriction endonuclease gene. The BssHII