The suckling mouse has been used as a model to identifyVibrio cholerae intestinal colonization factors for over two decades, yet little is known about the location of recoverable organisms along the gastrointestinal (GI) tract following intragastric inoculation. In the present study, we determined the population dynamics of wild-type and avirulent mutant derivatives of both classical and El Tor biotype strains throughout the entire suckling mouse GI tract at various times after intragastric inoculation. Wild-type strains preferentially colonized the middle small bowel with a sharp demarcation between more proximal segments which had manyfold-fewer recoverable cells. Surprisingly, large and stable populations of viable cells were also recovered from the cecum and large bowel. Strains lacking toxin-coregulated pili (TCP−) were cleared from the small bowel; however, an El Tor TCP−strain colonized the cecum and large bowel almost as well as the wild-type strain. Strains lacking lipopolysaccharide O antigen (OA−) were efficiently cleared from the small bowel at early times but then showed net growth for the remainder of the infections. Moreover, large populations of the OA− strains were maintained in the large bowel. These results show that for the El Tor biotype neither TCP nor OA is required for colonization of the suckling mouse large bowel. Finally, similar percent recoveries of wild-type, TCP−, and OA− strains from the small bowel at an early time after infection suggest that TCP and OA are not required for strains of either biotype to resist bactericidal mechanisms in the suckling mouse GI tract.
The iviVII gene of Vibrio cholerae was previously identified by a screen for genes induced during intestinal infection. In the present study, nucleotide sequence analysis revealed that iviVII is a 1,659-bp open reading frame, herein designated vieB, that is predicted to be last in a tricistronic operon (vieSAB). The deduced amino acid sequence of VieS exhibited similarity to the sensor kinase component, and those of VieA and VieB were similar to the response regulator components, respectively, of the two-component signal transduction family. Analysis of transcriptional fusions to a site-specific DNA recombinase reporter, tnpR, revealed that vieSand vieA are transcribed during in vitro growth in avieAB-independent and vieA-dependent manner, respectively. In contrast, transcription of vieB occurred exclusively during infection and was not dependent upon VieB. We conclude that the vieSAB genes are differentially regulated, at least during laboratory growth. Use of a V. cholerae strain harboring avieB::tnpR transcriptional fusion allowed the kinetics and location of vieB expression within the intestine to be determined. We found that vieBtranscription is induced shortly after infection of the proximal and mid-small intestine.
Acid adaptation has previously been shown to increase the infectivity of Vibrio cholerae in the infant mouse model. To better understand this phenomenon, we monitored the spatial distribution and temporal changes in the ratios of acid-adapted cells to unadapted V. cholerae cells in the small intestine, as well as the timing of virulence factor expression. We found that the competitive advantage afforded by acid adaptation does not become manifest until greater than 3 h postinfection; thus, acid adaptation does not increase V. cholerae passage through the gastric acid barrier. Additionally, acid-adapted and unadapted V. cholerae cells colonize the same sections of the small intestine and show similar kinetics of transcriptional induction of the virulence genes tcpA and ctxA. These studies suggest that the increased infectivity of acid-adapted V. cholerae is due to a more rapid onset of multiplication and/or to an increased multiplication rate within the infant mouse intestine.For oral route pathogens, such as Salmonella enterica serovar Typhimurium, Escherichia coli, and Vibrio cholerae, the ability to survive passage through the human gastric acid barrier is a crucial component of the bacterial life cycle. This ability is believed to be linked to an adaptive stress response to acid known as the acid tolerance response (ATR) (7, 9, 11). It is also possible that the ATR may enhance survival and growth within the intestinal tract after passage through the stomach. Analysis of V. cholerae has revealed a number of genes that play crucial roles in ATR (8-10). Additionally it was shown that ATR increases bacterial infectivity: specifically, acidadapted V. cholerae outcompeted unadapted V. cholerae by 1 order of magnitude after 24 h of coinfection in the infant mouse but did not outcompete the unadapted organism during in vitro growth (9). Mechanistically, this could be explained by increased survival during transit through the stomach, increased fitness within the small intestine, or a combination of the two. In this work, we investigate the nature of ATR-induced V. cholerae hyperinfectivity and observe a growth advantage of adapted versus unadapted V. cholerae cells at middle to late stages of a 24-h infection. In addition, we evaluate the primary sites of colonization of acid-adapted V. cholerae compared to those of unadapted cells and measure the effects of acid adaptation on the kinetics of transcriptional induction of two critical virulence factors, cholera toxin (CT) and toxincoregulated pilus (TCP).Gastric survival profile. To determine whether hyperinfectivity of acid-adapted V. cholerae was due to an increased ability to survive transit through the gastric barrier, we analyzed the temporal population dynamics during competition assays. In this assay, differentially marked acid-adapted and unadapted strains were coinfected into 5-day-old CD-1 infant mice as previously described (9). Briefly, overnight cultures of isogenic lacZ ϩ and lacZ mutant V. cholerae strains AC51 and AC168 (9) were subcultured to fresh Lu...
During meiosis, the alignment of homologous chromosomes facilitates their subsequent migration away from one another to opposite spindle poles at anaphase I. Recombination is part of the mechanism by which chromosomes identify their homologous partners, and serves to link the homologs in a way that, in some organisms, has been shown to promote proper attachment to the meiotic spindle. We have built a diploid strain that contains a pair of homeologous chromosomes V': one is derived from Saccharomyces cerevisiae and one originates from S. carlsbergensis. Sequence analysis reveals that these chromosomes share 71% sequence identity. The homeologs experience high levels of meiotic double-stranded breaks. Despite their relatedness and their competence to initiate recombination, the meiotic segregation behavior of the homeologous chromosomes suggests that, in most meioses, they are partitioned by a meiotic segregation system that has been shown previously to partition non-exchange chromosomes and pairs with no homology. Though the homeologous chromosomes show a degree of meiotic segregation fidelity similar to that of other non-exchange pairs, our data provide evidence that their limited sequence homology may provide some bias in meiotic partner choice.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.