The spoOJ gene of BaciUlus subtilis is required for the initiation of sporulation. We show that the sporulation defect caused by null mutations in spoOJ is suppressed by a null mutation in the gene located directly upstream from spoOJ, soj (suppressor of spoOJ). These results indicate that Soj inhibits the initiation of sporulation and that SpoOJ antagonizes that inhibition. Further genetic experiments indicated that Soj ultimately affects sporulation by inhibiting the activation (phosphorylation) of the developmental transcription factor encoded by spoOA. In addition, the temperature-sensitive sporulation phenotpe caused by the fts4279 (spoIIN279) mutation was partly suppressed by the soj null mutation, indicating that FtsA might also affect the activity of Soj. Soj and SpoOJ are known to be similar in sequence to a family of proteins involved in plasmid partitioning, including ParA and ParB of prophage P1, SopA and SopB of F, and IncC and KorB of RK2. spoOJ was found to be required for normal chromosome partitioning as well as for sporulation. spoOJ null mutants produced a significant proportion of anucleate cells during vegetative growth. The dual functions of SpoOJ could provide a mechanism for regulating the initiation of sporulation in response to activity of the chromosome partition machinery.The generation of new cells during growth or development requires proper replication, repair, and segregation of chromosomes. Conditions that perturb chromosome replication or damage DNA often inhibit cell cycle progression or development through checkpoint mechanisms. Such regulatory mechanisms are present in organisms as diverse as bacteria, yeasts, and mammals and act to prevent the unproductive formation of cells lacking intact chromosomes.Spore formation by the gram-positive bacterium Bacillus subtilis is a developmental process requiring two different cell types. Each cell type has an intact chromosome and a characteristic and distinct pattern of gene expression. The two cell types are created by formation of an asymmetric division septum early during development. The smaller cell, known as the forespore, develops into the mature spore while enclosed in the larger mother cell (30).One of the most important early events necessary for the initiation of sporulation is the activation of the developmental transcription factor encoded by spoOA. SpoOA is activated by phosphorylation, and SpoOA-P induces expression of several genes, including spoIL4, spoIIE, and spoIIG (4,6,46,47,55,58) that are essential for sporulation and the establishment of cell type-specific gene expression (30). Phosphorylation of SpoOA requires histidine protein kinases, i.e., KinA, -B, and -C (2, 27, 38, 56), and two phospho-transfer proteins, SpoOF and SpoOB (7). The histidine protein kinases autophosphorylate on a histidine residue, and phosphate is transferred to SpoOF, and then from

Extraintestinal pathogenic Escherichia coli (ExPEC) possesses virulence traits that allow it to invade, colonize, and induce disease in bodily sites outside of the gastrointestinal tract. Human diseases caused by ExPEC include urinary tract infections, neonatal meningitis, sepsis, pneumonia, surgical site infections, as well as infections in other extraintestinal locations. ExPEC-induced diseases represent a large burden in terms of medical costs and productivity losses. In addition to human illnesses, ExPEC strains also cause extraintestinal infections in domestic animals and pets. A commonality of virulence factors has been demonstrated between human and animal ExPEC, suggesting that the organisms are zoonotic pathogens. ExPEC strains have been isolated from food products, in particular from raw meats and poultry, indicating that these organisms potentially represent a new class of foodborne pathogens. This review discusses various aspects of ExPEC, including its presence in food products, in animals used for food or as companion pets; the diseases ExPEC can cause; and the virulence factors and virulence mechanisms that cause disease.

Rhamnolipids, naturally occurring biosurfactants constructed of rhamnose sugar molecules and ␤-hydroxyalkanoic acids, have a wide range of potential commercial applications. In the course of a survey of 33 different bacterial isolates, we have identified, using a phenotypic assay for rhamnolipid production, a strain of the nonpathogenic bacterial species Pseudomonas chlororaphis that is capable of producing rhamnolipids. Rhamnolipid production by P. chlororaphis was achieved by growth at room temperature in static cultures of a mineral salts medium containing 2% glucose. We obtained yields of roughly 1 g/liter of rhamnolipids, an amount comparable to the production levels reported in Pseudomonas aeruginosa grown with glucose as the carbon source. The rhamnolipids produced by P. chlororaphis appear to be exclusively the mono-rhamnolipid form. The most prevalent molecular species had one monounsaturated hydroxy fatty acid of 12 carbons and one saturated hydroxy fatty acid of 10 carbons. P. chlororaphis, a nonpathogenic saprophyte of the soil, is currently employed as a biocontrol agent against certain types of plant fungal diseases. The pathogenic nature of all bacteria previously known to produce rhamnolipids has been a major obstacle to commercial production of rhamnolipids. The use of P. chlororaphis therefore greatly simplifies this matter by removing the need for containment systems and stringent separation processes in the production of rhamnolipids.

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Type 1 fimbria is a proven virulence factor of uropathogenic Escherichia coli (UPEC), causing urinary tract infections. Expression of the fimbria is regulated at the transcriptional level by a promoter situated on an invertible element, which can exist in one of two different orientations. The orientation of the invertible element that allows the expression of type 1 fimbriae is defined as "on," and the opposite orientation, in which no transcription occurs, is defined as "off." During the course of a urinary tract infection, we have observed that the infecting E. coli population alternates between fimbriated and nonfimbriated states, with the fimbriated on orientation peaking at 24 h. We propose that the ability of the invertible element to switch orientations during infection is itself a virulence trait. To test this hypothesis, nucleotide sequence changes were introduced in the left inverted repeat of the invertible element of UPEC pyelonephritis strain CFT073 that locked the invertible elements permanently in either the on or the off orientation. The virulence of these mutants was assessed in the CBA mouse model of ascending urinary tract infection at 4, 24, 48, and 72 h postinoculation (hpi). We conducted independent challenges, in which bladders of mice were inoculated with either a single mutant or the wild type, and cochallenges, in which a mutant and the wild type were inoculated together to allow direct competition in the urinary tract. In both sets of experimental infections, the locked-off mutant was recovered from the urine, bladder, and kidneys in significantly lower numbers than the wild type at 24 hpi (P < 0.05), demonstrating its attenuation. Conversely, the locked-on mutant was recovered in higher numbers than the wild type at 24 hpi (P < 0.05), showing enhanced virulence of this mutant. No significant differences were seen between the mutants and wild type in the urine or the bladder at 48 or 72 hpi. However, the wild type outcompeted the locked-off mutant in the kidneys during the cochallenge experiment at 72 hpi (P ‫؍‬ 0.009). Overall, these data suggest that the ability of the invertible element controlling type 1 fimbria expression to phase vary contributes significantly to virulence early (24 hpi) in the course of a urinary tract infection by UPEC and most profoundly influences colonization of the bladder.

Escherichia coli is the primary cause of uncomplicated infections of the urinary tract including cystitis. More serious infections, characterized as acute pyelonephritis, can also develop. Type 1 fimbriae of E. coli contribute to virulence in the urinary tract; however, only recently has the expression of the type 1 fimbriae been investigated in vivo using molecular techniques. Transcription of type 1 fimbrial genes is controlled by a promoter that resides on a 314-bp invertible element capable of two orientations. One places the promoter in the ON orientation, allowing for transcription; the other places the promoter in the OFF orientation, preventing transcription. A PCR-based assay was developed to measure the orientation of the invertible element during an experimental urinary tract infection in mice. Using this assay, it was found that the percentage of the population ON in urine samples correlated with the respective CFU per gram of bladder (P ‫؍‬ 0.0006) but not with CFU per gram of kidney (P > 0.069). Cystitis isolates present in the urine of mice during the course of infection had a higher percentage of their invertible elements in the ON orientation than did pyelonephritis isolates (85 and 34%, respectively, at 24 h; P < 0.0001). In general, cystitis isolates, unlike pyelonephritis isolates, were more likely to maintain their invertible elements in the ON orientation for the entire period of infection. E. coli cells expressing type 1 fimbriae, expelled in urine, were shown by scanning electron microscopy to be densely packed on the surface of uroepithelial cells. These results suggest that expression of type 1 fimbriae is more critical for cystitis strains than for pyelonephritis strains in the early stages of an infection during bladder colonization.

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In Escherichia coli O157:H7 strain ATCC 43895, a guanine-to-thymine transversion in the csgD promoter created strain 43895OR. Strain 43895OR produces an abundant extracellular matrix rich in curli fibers, forms biofilms on solid surfaces, invades cultured epithelial cells, and is more virulent in mice than strain 43895. In this study we compared the formic acid-soluble proteins expressed by strains 43895OR and 43895 using one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis and identified two differentially expressed proteins. A 17-kDa protein unique to strain 43895OR was identified from matrix-assisted laser desorption ionization-time of flight analysis combined with mass spectrometry (MS) and tandem MS (MS/MS) as the curli subunit encoded by csgA. A <10-kDa protein, more highly expressed in strain 43895, was identified as the Lpp lipoprotein. Mutants of strain 43895OR with disruption of lpp, csgA, or both lpp and csgA were created and tested for changes in phenotype and function. The results of this study show that both Lpp and CsgA contribute to the observed colony morphology, Congo red binding, motility, and biofilm formation. We also show that both CsgA and Lpp are required by strain 43895OR for the invasion of cultured HEp-2 cells. These studies suggest that in strain 43895OR, the murein lipoprotein Lpp indirectly regulates CsgA expression through the CpxAR system by a posttranscriptional mechanism.Escherichia coli serotype O157:H7 is estimated to cause more than 73,000 illnesses per year in the United States (26). From 1982 to 2002, beef products (e.g., ground beef) were the most common vehicle for food-borne outbreaks associated with serotype O157:H7 and were more than twice as common as produce-associated outbreaks during that same period (26). Despite concentrated efforts to improve sanitation and dressing procedures within slaughter and processing plants, contamination with and persistence of E. coli O157:H7 within plants remains a paramount problem. In addition to instances of illness, during 2007 alone, E. coli O157:H7 contamination led to the recall of more than 27 million lb. of beef (1).Biofilm formation can enhance the persistence of food pathogens on plant and processing surfaces and serve as a source of product contamination (21). Within the gut, biofilms may develop as coexisting commensal and pathogenic strains of E. coli (2, 4). The production of curli fimbriae and the exopolysaccharide cellulose are arguably the most common contributors to biofilm formation by Escherichia coli and Salmonella spp. In human commensal E. coli isolates, 46 to 79% of the isolates produced curli, cellulose, or both components depending on temperature (2). Those strains expressing either one or both of these components had medium to high biofilmforming capabilities.In E. coli and Salmonella spp., the coexpression of curli and cellulose leads to an aggregative colony phenotype (rdar; red, dry, and rough) when grown on medium containing Congo red dye (32,40). Inactivation of the cellul...