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Lysogeny at Mid-Twentieth Century: P1, P2, and Other Experimental Systems. Giuseppe Bertani, 2004. The nptA Gene of Vibrio cholerae Encodes a Functional Sodium-Dependent Phosphate Cotransporter Homologous to the Type II Cotransporters of Eukaryotes. Michael Lebens, 2002.The nptA gene of Vibrio cholerae has significant protein sequence homology with type II sodium-dependent phosphate (Pi) cotransporters found in animals but not previously identified in prokaryotes . The phylogeny of known type II cotransporter sequences indicates that nptA may be either an ancestral gene or a gene acquired from a higher eukaryotic source . The gene was cloned into an expression vector under the control of an inducible promoter and expressed in Escherichia coli . The results demonstrate that nptA encodes a functional protein with activity similar to that of the animal enzyme, catalyzing high-affinity, sodium-dependent Pi uptake with comparable affinities for both sodium and phosphate ions . Furthermore, the activity of NptA is influenced by pH, again in a manner similar to that of the NaPi-2a subtype of the animal enzyme, although it lacks the corresponding REK motif thought to be responsible for this phenomenon . Pi uptake activity, a component of which appeared to be sodium dependent, was increased in V . cholerae by phosphate starvation . However, it appears from the use of a reporter gene expressed from the nptA promoter that none of this activity is attributable to the induction of expression from nptA . It is thus proposed that the physiological function of NptA protein may be the rapid uptake of Pi in preparation for rapid growth in nutrient-rich environments and that it may therefore play a role in establishing infection . Mannitol-1-Phosphate Dehydrogenase (MtlD) Is Required for Mannitol and Glucitol Assimilation in Bacillus subtilis: Possible Cooperation of mtl and gut Operons. Shouji Watanabe, 2003.We found that mannitol-1-phosphate dehydrogenase (MtlD), a component of the mannitol-specific phosphotransferase system, is required for glucitol assimilation in addition to GutR, GutB, and GutP in Bacillus subtilis . Northern hybridization of total RNA and microarray studies of RNA from cells cultured on glucose, mannitol, and glucitol indicated that mannitol as the sole carbon source induced hyperexpression of the mtl operon, whereas glucitol induced both mtl and gut operons . The B . subtilis mtl operon consists of mtlA (encoding enzyme IICBAmt1) and mtlD, and its transcriptional regulator gene, mtlR, is located 14.4 kb downstream from the mtl operon on the chromosome . The mtlA, mtlD, and mtlR mutants disrupted by the introduction of the pMUTin derivatives MTLAd, MTLDd, and MTLRd, respectively, could not grow normally on either mannitol or glucitol . However, the growth of MTLAd on glucitol was enhanced by IPTG (isopropyl-ß-D-thiogalactopyranoside) . This mutant has an IPTG-inducible promoter (Pspac promoter) located in mtlA, and this site corresponds to the upstream region of mtlD . Insertion mutants of mtlD harboring the chloramphenicol resistance gene also could not grow on either mannitol or glucitol . In contrast, an insertion mutant of mtlA could grow on glucitol but not on mannitol in the presence or absence of IPTG . MtlR bound to the promoter region of the mtl operon but not to a DNA fragment containing the gut promoter region . Direct Detection of Vibrio cholerae and ctxA in Peruvian Coastal Water and Plankton by PCR. Erin K. Lipp, 2003.Seawater and plankton samples were collected over a period of 17 months from November 1998 to March 2000 along the coast of Peru . Total DNA was extracted from water and from plankton grouped by size into two fractions (64 µm to 202 µm and >202 µm) . All samples were assayed for Vibrio cholerae, V . cholerae O1, V . cholerae O139, and ctxA by PCR . Of 50 samples collected and tested, 33 (66.0%) were positive for V . cholerae in at least one of the three fractions . Of these, 62.5% (n = 32) contained V . cholerae O1; ctxA was detected in 25% (n = 20) of the V . cholerae O1-positive samples . None were positive for V . cholerae O139 . Thus, PCR was successfully employed in detecting toxigenic V . cholerae directly in seawater and plankton samples and provides evidence for an environmental reservoir for this pathogen in Peruvian coastal waters . Oriented Adhesion of Escherichia coli to Polystyrene Particles. Joseph F. Jones, 2003.The adhesion of nonflagellated Escherichia coli strain K-12 to polystyrene (PS) latex spheres or glass capillaries has been observed by using several techniques . Attention was focused on the orientation of the rod-shaped bacteria as they adhered to the surfaces in 100 mM phosphate-buffered saline . Data show that PS particles adhered to the ends of the bacteria more than 90% of the time . Moreover, the PS particles adhered to one end only, never to both . Similarly, for experiments with bacteria adhering to glass, the bacteria adhered on their ends . In order to determine whether the end of a bacterium had a different charge density from that of the middle, rotational electrophoresis experiments were used . These experiments indicated no measurable charge nonuniformity . In order to examine how strongly adhered the bacteria were to the PS particles, differential electrophoresis was used . Almost always, bacteria were found to be irreversibly adhered to the PS spheres . The cause of the oriented adhesion is not likely due to surface lipopolysaccharides (LPS), since the three strains of K-12 that were used, each having a different length of LPS, showed similar behavior . The results are discussed in terms of bacterial cell polarity . The data indicate that nanodomains on the bacterial ends are important for adhesion and that the time scale for irreversible adhesion is short .
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