A Single Nucleotide Change Affects Fur-Dependent Regulation of sodB in H. pylori

Helicobacter pylori is a significant human pathogen that has adapted to survive the many stresses found within the gastric environment. Superoxide Dismutase (SodB) is an important factor that helps H. pylori combat oxidative stress. sodB was previously shown to be repressed by the Ferric Uptake Regulator (Fur) in the absence of iron (apo-Fur regulation) [1]. Herein, we show that apo regulation is not fully conserved among all strains of H. pylori. apo-Fur dependent changes in sodB expression are not observed under iron deplete conditions in H. pylori strains G27, HPAG1, or J99. However, Fur regulation of pfr and amiE occurs as expected. Comparative analysis of the Fur coding sequence between G27 and 26695 revealed a single amino acid difference, which was not responsible for the altered sodB regulation. Comparison of the sodB promoters from G27 and 26695 also revealed a single nucleotide difference within the predicted Fur binding site. Alteration of this nucleotide in G27 to that of 26695 restored apo-Fur dependent sodB regulation, indicating that a single base difference is at least partially responsible for the difference in sodB regulation observed among these H. pylori strains. Fur binding studies revealed that alteration of this single nucleotide in G27 increased the affinity of Fur for the sodB promoter. Additionally, the single base change in G27 enabled the sodB promoter to bind to apo-Fur with affinities similar to the 26695 sodB promoter. Taken together these data indicate that this nucleotide residue is important for direct apo-Fur binding to the sodB promoter.     

Mate choice copying and conspecific cueing in Japanese quail, Coturnix coturnix japonica

In four experiments, we examined the effects on the affiliative preferences of 'focal' female Japanese quail given the opportunity to watch a conspecific male interact with a 'model' female. Experiments were conducted in three, 10-min phases: (1) a pretest, during which a 'focal' female chose between two males; (2) an observation phase, when each focal female watched the male she had spent less time near during the pretest (her 'nonpreferred' male) interact with a 'model' quail; and (3) a post-test, during which each focal female again chose between her nonpreferred and preferred males. Focal females increased their preferences for nonpreferred males after seeing them together with a model female (but not a model male), even if the nonpreferred male and model female were separated by an opaque barrier that prevented them from interacting. A focal female's preference for the end of the enclosure containing her nonpreferred male was not increased when she either watched him court a concealed model female or watched a model female that was being courted by him. Taken together, the present results suggest that a simple tendency for females to approach areas where they have previously seen a male and female quail, in preference to locations where they have seen only a male quail, can explain some of the effect of watching a nonpreferred male mate on a female's tendency to affiliate with him. However, focal females also showed enhanced preferences for nonpreferred males they had seen mating after we both moved those males and controlled for effects of transposition. Thus, processes akin to both 'mate choice copying' and 'conspecific cueing' remain viable explanations for the increase in a focal female quail's tendency to affiliate with a male she watched mate with another female. Copyright 1999 The Association for the Study of Animal Behaviour.     

Factors affecting the survival of sheep embryos after transfer within a MOET program

Multiple ovulation and embryo transfer (MOET) has the potential to increase the rate of genetic improvement in sheep. However, better realization of this potential requires maximum survival rates of transferred embryos of high genetic merit after transfer into recipient ewes. These studies were therefore conducted to investigate the effect of both embryonic and recipient ewe factors on the survival rate of transferred embryos. Survival rate was similar after transfer of morula or blastocyst stage embryos, and these were higher (P<0.05) than for very early morulae and early morulae. Advanced embryos (Day 5 blastocyst) had an advantage (P<0.05) in survival rate over retarded embryos (Day 6 morula). Grades 1 and 2 embryos survived significantly (P<0.05) better than Grades 3 or 4 embryos. There was no difference in embryo survival rate following transfer to recipients with different numbers of corpora lutea. In general, age or parity of recipient ewes did not affect embryo survival rate, although a higher (P<0.05) embryo survival rate was observed for yearling recipients. Buserelin (GnRH agonist) treatment of recipient ewes 5 or 6 days after transfer of embryos (Day 12 of the cycle) did not improve embryo survival rate. These results confirm that both embryonic and recipient factors can play an important role in the success of a MOET program in sheep.     

Acid tolerance of gastrointestinal pathogens

The ability of pathogenic bacteria to survive in the face of host defense systems is intimately linked to virulence. This is exemplified by gastrointestinal pathogens that must survive exposure to extreme acid conditions within the stomach and organic acid conditions within the small intestine. These organisms have evolved complex systems to respond to acid stress, and recent work has revealed new genetic components involved in survival and virulence. Here, we review recent work on four gastrointestinal pathogens, focusing on studies that reveal both acid-inducible resistance systems and inherent (basal state) acid-resistance systems.     

Activation of the bgl operon by adaptive mutation

In growing Escherichia coli K12 cells, the cryptic bgl operon is activated 98% of the time by insertions of IS1 or IS5 into the control region, designated bglR. The activated bgl operon permits utilization of the beta-glucoside sugar arbutin as a sole carbon and energy source. The bgl operon is also activated by late-occurring mutations during prolonged selection on arbutin. The late-occurring mutations that occurred during prolonged carbon starvation in the presence of arbutin were "adaptive mutations" because they were specific to the presence of arbutin, and they did not occur during prolonged starvation in the absence of arbutin. The spectrum of late-arising mutations differed from that of early-arising, growth-dependent mutations in that 20% of the late-arising mutants resulted from mutations at the hns locus. This provides the first direct evidence for adaptive mutagenesis mediated by the insertion of IS elements. Because no special genetic background is required to select Bgl+ mutants, this affords the opportunity to study IS-element-mediated adaptive mutagenesis in a variety of genetic backgrounds, including the backgrounds of natural isolates of E. coli.      

Inhibition of L- and P-selectin by a rationally synthesized novel core 2-like branched structure containing GalNAc-Lewisx and Neu5Acalpha2- 3Galbeta1-3GalNAc sequences

The selectins interact in important normal and pathological situations with certain sialylated, fucosylated glycoconjugate ligands containing sialyl Lewisx(Neu5Acalpha2-3Galbeta1-4(Fucalpha1-3)GlcN Ac). Much effort has gone into the synthesis of sialylated and sulfated Lewisxanalogs as competitive ligands for the selectins. Since the natural selectin ligands GlyCAM-1 and PSGL-1 carry sialyl Lewisxas part of a branched Core 2 O-linked structure, we recently synthesized Galbeta1-4(Fucalpha1-3)GlcNAcbeta1-6(SE-3Galbeta1++ +-3)GalNAc1alphaOMe and found it to be a moderately superior ligand for L and P-selectin (Koenig et al. , Glycobiology 7, 79-93, 1997). Other studies have shown that sulfate esters can replace sialic acid in some selectin ligands (Yeun et al. , Biochemistry, 31, 9126-9131, 1992; Imai et al. , Nature, 361, 555, 1993). Based upon these observations, we hypothesized that Neu5Acalpha2-3Galbeta1-3GalNAc might have the capability of interacting with L- and P-selectin. To examine this hypothesis, we synthesized Galbeta1-4(Fucalpha1-3)GlcNAcbeta1-6(Neu5Acalpha2++ +-3Galbeta1-3)- GalNAc alpha1-OB, which was found to be 2- to 3-fold better than sialyl Lexfor P and L selectin, respectively. We also report the synthesis of an unusual structure GalNAcbeta1-4(Fucalpha1- 3)GlcNAcbeta1-OMe (GalNAc- Lewisx-O-methyl glycoside), which also proved to be a better inhibitor of L- and P-selectin than sialyl Lewisx-OMe. Combining this with our knowledge of Core 2 branched structures, we have synthesized a molecule that is 5- to 6-fold better at inhibiting L- and P-selectin than sialyl Lewisx-OMe, By contrast to unbranched structures, substitution of a sulfate ester group for a sialic acid residue in such a molecule resulted in a considerable loss of inhibition ability. Thus, the combination of a sialic acid residue on the primary (beta1-3) arm, and a modified Lexunit on the branched (beta1-6) arm on an O-linked Core 2 structure generated a monovalent synthetic oliogosaccharide inhibitor superior to SLexfor both L- and P-selectin.      

Aeromonas sobria in chlorinated drinking water supplies

Aeromonas species were recovered from over 27% of 183 chlorinated drinking water samples collected during an 18-month period. Sixteen of 20 isolates tested elicited a cytotoxic response by Y-1 mouse adrenal cells. None of the strains was either enterotoxigenic by the rabbit ligated ileal loop assay, exhibited piliation, or showed significant mannose resistant adherence to human buccal cells. TheAeromonas isolates were further identified to beA. sobria and were resistant to ampicillin and susceptible to chloramphenicol, kanamycin, streptomycin, and tetracycline. Total coliform levels did not correlate withAeromonas densities in distribution water. With 85% of the samplings,Aeromonas occurred in distribution water when no coliforms were detectable by either the membrane filter or most-probable-number techniques. A significant correlation (P<.001) existed between standard plate count levels andAeromonas.