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Candida albicans mutants lacking the cell wall biosynthesis kinase 1 form large aggregates and are unable to undergo morphological differentiation. Results show that the mutants exhibit altered expression pattern of many cell wall associated proteins.

The mechanism of deoxycytosine methylase mediated mutagenesis in vivo is examined in Escherichia coli under conditions of reduced S-adenosylmethionine. Data indicate that cells show an increased C-to-T mutagenesis resulting in a filamentous phenotype in minimal medium.

Results show that by exposing to toxic levels of carboxymuconate spontaneous mutations can be effected in Agrobacterium tumefaciens gene encoding protocatechuate 3,4-dioxygenase. Complete sequence data of the genes pcaH, pcaG, and pcaB of A. tumefaciens A348 are presented.

Research was conducted to understand the role of the two-component ResD-ResE signal transduction system in the respiratory metabolism of Bacillus subtilis. Results show glycolytic intermediate 1,3-diphosphoglycerate activate ResD independent of ResE as revealed by an ResE mutant strain.

Results show that pleiotropic effect locus (pel) of Streptococcus pyogenes mediates coordinated regulation of secreted and surface associated M and M-related proteins as demonstrated by the analysis of pel mutants.

The null mutations of mecA and mecB reduce the expressions of sigD and autolysin genes in Bacillus subtilis and affect the synthesis of flagellin protein, encoded by sigD-dependent hag gene. The effect of mec genes on the expression of the autolysin genes is due to sigD protein level rather than the involvement of ComK protein. The transcription of the sigD is affected either directly or indirectly by mecA and mecB proteins. The mec proteins play two roles in motility, one of which is sigD dependent.

Extracellular acidity induces the transcription of a tandem promoter P2 which initiates transcription in virG gene in Agrobacterium tumefaciens. An assay of a series of 5' and 3' resections and site-directed nucleotide substitutions allows the identification of cis-acting sites responsible for P2 activity. The nucleotides between positions -9 and -37 enable regulated promoter activity. The P2 expression significantly reduces with nucleotide substitutions at -10 and -35 regions and promoter activity reduces with changes between -24 and -32 nucleotides.

Molecular characterization of the avrBs2 gene from Xanthomonas campestris pv. vesicatoria reveals that the gene expression generates disease resistance in Bs2 pepper plant and controls the pathogen virulence. The gene has an open reading frame, which encodes the 80.1-kDa protein. The two classes of Xanthomonas pathogens, one having 5-bp insertion and the second class having a divergent 3' region, are mutated in avrBs2 gene. The study of agrocinopine synthase along with avirulence and virulence gives several models for the function of AvrBs2.

A mutational analysis of transmembrane segments (TM) of a bacterial chemoreceptor, Trg, reveals that a few positions at which substitutions alter functions or induce signaling. These substitutions show a helical face for TM2, which is directed into the protein interior of the transmembrane domain. The movement between TM2 and TM1 gives the conformational signaling, which is optimal when interactions stabilize across the interface between the homologous helix in the transmembrane domain.

An analysis of the structural defects of nonsporulating mutants of Streptomyces griseus reveals that the class III mutants develop sporulation septa and thick spore walls prematurely. The wild-type strain develops sporogenic hyphae, nucleoid segregation and thickening of the spore wall during maturation. The class III mutants are defective in the regulation of the key events of morphogenesis of Streptomyces.

Dominant negative activity of mutants of the Escherichia coli nucleoid-associated protein, H-NS, can be explained on the basis of formation of hybrid species with compromised function. The mutants are defective in promoter repression activity in an H-NS-free strain, and obstruct the repression activity of H-NS. Domain organizations and functions in StpA and H-NS are related closely. Cross-talk between native H-NS and StpA takes place by protein-protein interaction, rather than occurring at specific promoters only.

The incorporation of an aminoglycoside 3'-phosphotransferase gene into one of the three copies of the hao gene encoding hydroxylamine oxidoreductase induces mutagenesis in the aerobic bacteria Nitrosomonas europaea. Electroporation and homologous recombination transform the cells. The mutant cells are phenotypically similar to the wild type cells. This indicates that the active hao genes compensate for a mutation in one hao gene. The mutant cells are stable even when there is no kanamycin-selective pressure.

A decreased capacity of multiple-peptidase mutants of Lactococcus lactis, to break down peptides to free amino acids, leads to a reduction in their ability to grow in milk. An increase in the number of peptidase gene mutants leads to a lesser growth rate in milk giving rise to smaller amounts of intracellular amino acids. Single deficiencies in the genes, however, PepX, PepO, PepC, and PepT, barring PepN produce little effect on the growth rates of the mutants in milk.

The C-terminal end of the Salmonella enterica wbaP gene controls the initial galactosyltransferase (GT) step of O-antigen synthesis as wbaP with an intact C-terminal and a mutant N-terminal retains GT activity. The C-terminal controls the transfer of galactosyl-1-phosphate from GDP-galactose to undecaprenyl phosphate. The N-terminal controls the later stage (T) of the synthesis which involves the release of undecaprenyl pyrophosphate-Gal from WbaP. The T stage occurs before the O-antigen flips from the cytoplasmic end to the periplasmic end of the cytoplasmic membrane.

The Salmonella typhimurium mouse virulence gene, mviA, controls the stability of the RpoS protein, which induces the production of acid shock proteins (ASPs). The increased formation of ASPs stimulates the development of acid tolerance in virulent strains of S. typhimurium. Mutations in mviA increase the formation of ASPs and the tolerance to acid, heat, and osmotic stress. The mutations decrease the growth rate and colony size of the bacteria. Mutations in rpoS reverse the effects of mviA mutations.

The glucose uptake and stimulation of invertase activity in Saccharomyces cerevisiae requires the activity of more than one gene encoding the hexose transporter proteins (HTX). Mutations in the HTX genes change glucose repression and the affinity and rate of glucose transport. Growth on glucose comparable to the wild-type growth rate is seen in mutant CY294, which contains the HTX6/7 gene but lacks the SNF3 and HXT1-4 genes. Glucose transport and invertase activity is unaffected by glucose in this mutant. Glucose sensitivity is restored by the SNF3 or HTX2 gene in multiple mutants.

Mutational analysis of the Escherichia coli phosphocarrier protein, HPr, using kinetic approaches revealed that sequential phosphoryl transfer in the phosphoenolpyruvate:sugar phosphotransferase system is no significantly affected by mutations. However, changes in the affinities for phospho-Hpr of the permeases of this system, sugar-specific enzymes II, repress the production of beta-glucosides without affecting maximal reaction rates. It is suggested that certain residues in Hpr influence its conformation, which in turn, affects a variety of physiological processes.

Early screens for conditional lethal mutations that affected rRNA expression in Escherichia coli identified temperature-sensitive fda mutants (fda encodes the glycolytic enzyme fructose-l,6-diphosphate aldolase). It was shown that these fda(Ts) mutants were severely impaired in rRNA synthesis upon shift to the restrictive temperature, although the mechanism of inhibition was never determined. Here, we bring resolution to this long-standing question by showing that changes in the concentrations of guanosine 5'-diphosphate 3'-diphosphate and initiating nucleoside triphosphates can account for the previously observed effects of fda mutations on rRNA transcription.

An oxygen-insensitive nitroreductase of Escherichia coli, NfsB, can be converted to an FRase I-like flavin reductase (FRase I). A single amino acid substitution in the least-conserved region allows the conversion. The activity of the FRase I is three times more than the major FRase I in Vibrio fischeri. The amino acid sequence of the two has significant similarity. The genes encoding the two bacterial reductases may have common a progenitor.

The exchange of codons with synonymous codons decreases the mRNA level and half-life of the Escherichia coli outer membrane protein A (ompA) gene at 37 degrees celsius, and enhances the beta-lactamase (bla) mRNA half-life. The mRNA turnover and amount is probably due to ribosomal traffic. The turnover process of ompA mRNA is growth temperature dependent. The results of the study show that ribosomes protect the ompA mRNA against endoribonucleases.

Research shows that alkyl hydroperoxide reductase protects Xanthomonas campestris pv. phaseoli against the toxicity of superoxide compounds by producing organic peroxide production. Data indicate that the enzyme protects the cells from menadione toxicity as catalase and superoxide dismutase can not give protection.