Strains were constructed that contain mutational alterations affecting two distinct functional domains within the araC gene protein. The araCi (catabolite repression insensitivity) and araCh (catabolite repression hypersensitivity) mutations were used to alter the catabolite repression sensitivity domain, and mutation to D-fucose resistance was used to alter the inducer binding domain. araCh, D...

Prophage P4 immunity is elicited by a short, 69-nucleotide RNA (CI RNA) coded for within the untranslated leader region of the same operon it controls. CI RNA causes termination of transcription that starts at the promoter PLE and prevents the expression of the distal part of the operon that codes for P4 replication functions (alpha operon). In this work, we identify two sequences in the untran...

Caulobacter crescentus performs chemotaxis by short intermittent reversals of rotation of its single polar flagellum. Tn5 insertions causing a general chemotaxis phenotype, an inability to reverse swimming direction and to form large swarm colonies, have been mapped to an 8-kb region of the C. crescentus genome. These Tn5 mutations had different effects on the methyl-accepting chemotaxis protei...

At least four genetically distinct classes of mutations give rise to triazolealanine resistance in SaZmoneZZa typhimurium. Each class studied affects regulation of the histidine operon. Mutants of one class, GO, are located at one end of the histidine operon. This class may be similar to operator constitutive mutants studied in other systems. At least two genetic sites are present in this regio...

conclusion our results showed that obtained protein patterns of the isolated strains were more reliable than serotyping results for typing purposes. our findings indicated that pap adhesion–encoding operon has an important role in the development and severity of uti. many cases of serious urogenital diseases are caused by a limited number of uropathogenic e.coli strains that generally possess s...

Carbon Storage Regulator A (CsrA) is an RNA binding protein that acts as a global regulator of diverse genes. Using a combination of genetics and biochemistry we show that CsrA binds directly to the 5' end of the transcript encoding AcrAB. Deletion of csrA or mutagenesis of the CsrA binding sites reduced production of both AcrA and AcrB. Nucleotide substitutions at the 5' UTR of acrA mRNA that ...

In Salmonella typhimurium, thiamine is a required nutrient that is synthesized de novo. Labeling studies have demonstrated probable precursors for both the 4-amino-5-hydroxymethyl-2-methylpyrimidine pyrophosphate moiety and the 4-methyl-5-(beta-hydroxyethyl) thiazole monophosphate moiety. The isolation of thiamine auxotrophs with mutations in at least five different genetic loci is reported. Th...

I N addition to their role in protein synthesis, aminoacyl tRNA synthetases in bacteria have been shown to have a regulatory role in the formation of enzymes involved in the synthesis of corresponding amino acids. This has been demonstrated at least in the case of isoleucine and valine (EIDLIC and NEIDHARDT 1965; YANIV, JACOB and GROS 1965) and histidine (SCHLESINGER and MAGASANIK 1964; ROTH, A...

Point mutations conferring resistance to fluoroquinolones were introduced in the gyr genes of the reference strain Clostridium difficile 630. Only mutants with the substitution Thr-82→Ile in GyrA, which characterizes the hypervirulent epidemic clone III/027/NAP1, were resistant to all fluoroquinolones tested. The absence of a fitness cost in vitro for the most frequent mutations detected in res...

There are two closely related hik31 operons involved in signal transduction on the chromosome and the pSYSX plasmid in the cyanobacterium Synechocystis sp. strain PCC 6803. We studied the growth, cell morphology, and gene expression in operon and hik mutants for both copies, under different growth conditions, to examine whether the duplicated copies have the same or different functions and gene...