scholarly journals rpoS Mutants in Archival Cultures ofSalmonella enterica Serovar Typhimurium

2000 ◽  
Vol 182 (16) ◽  
pp. 4375-4379 ◽  
Author(s):  
Amy Sutton ◽  
Raphael Buencamino ◽  
Abraham Eisenstark
Keyword(s):  
Point Mutations ◽  
Growth Conditions ◽  
Amino Acid Sequences ◽  
Start Codon ◽  
Wild Type ◽  
Term Survival ◽  
Bacterial Populations ◽  
Genetic Changes ◽  
Serovar Typhimurium

ABSTRACT Long-term survival under limited growth conditions presents bacterial populations with unique environmental challenges. The existence of Salmonella enterica serovar Typhimurium cultures undisturbed in sealed nutrient agar stab vials for 34 to 45 years offered a unique opportunity to examine genetic variability under natural conditions. We have initiated a study of genetic changes in these archival cultures. We chose to start with examination of therpoS gene since, among gram-negative bacteria, many genes needed for survival are regulated by RpoS, the stationary-phase sigma factor. In each of 27 vials examined, cells had the rpoSstart codon UUG instead of the expected AUG of Salmonellaand Escherichia coli strains recorded in GenBank. Ten of the 27 had additional mutations in the rpoS gene compared with the X77752 wild-type strain currently recorded in GenBank. TherpoS mutations in the 10 strains included two deletions as well as point mutations that altered amino acid sequences substantially. Since these stored strains were derived from ancestral cells inoculated decades ago and remained undisturbed, it is assumed that the 10 rpoS mutations occurred during storage. Since the remaining 17 sequences were wild type (other than in the start codon), it is obvious that rpoS remained relatively stable during decades of sealed storage.

scholarly journals Mechanism and Fitness Costs of PR-39 Resistance in Salmonella enterica Serovar Typhimurium LT2

2008 ◽  
Vol 52 (8) ◽  
pp. 2734-2741 ◽  
Author(s):  
Maria Pränting ◽  
Aurel Negrea ◽  
Mikael Rhen ◽  
Dan I. Andersson
Keyword(s):  
Antimicrobial Peptides ◽  
Salmonella Enterica ◽  
Culture Medium ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Wild Type ◽  
Term Survival ◽  
Resistance Development ◽  
Serovar Typhimurium ◽  
Reduced Rate

ABSTRACT PR-39 is a porcine antimicrobial peptide that kills bacteria with a mechanism that does not involve cell lysis. Here, we demonstrate that Salmonella enterica serovar Typhimurium can rapidly acquire mutations that reduce susceptibility to PR-39. Resistant mutants appeared at a rate of 0.4 × 10−6 per cell per generation. These mutants were about four times more resistant than the wild type and showed a greatly reduced rate of killing. Genetic analysis revealed mutations in the putative transport protein SbmA as being responsible for the observed resistance. These sbmA mutants were as fit as the wild-type parental strain as measured by growth rates in culture medium and mice and by long-term survival in stationary phase. These results suggest that resistance to certain antimicrobial peptides can rapidly develop without an obvious fitness cost for the bacteria and that resistance development could become a threat to the efficacy of antimicrobial peptides if used in a clinical setting.

scholarly journals Chromosomal Rearrangements in Salmonella enterica Serovar Typhi Strains Isolated from Asymptomatic Human Carriers

mBio ◽  
2011 ◽  
Vol 2 (3) ◽  
Author(s):  
T. David Matthews ◽  
Wolfgang Rabsch ◽  
Stanley Maloy
Keyword(s):  
Salmonella Enterica ◽  
Large Scale ◽  
Chromosomal Rearrangements ◽  
Growth Conditions ◽  
Genetic Changes ◽  
Content Type ◽  
Long Term Storage ◽  
Bacterial Chromosomes ◽  
Over Time

ABSTRACTHost-specific serovars ofSalmonella entericaoften have large-scale chromosomal rearrangements that occur by recombination betweenrrnoperons. Two hypotheses have been proposed to explain these rearrangements: (i) replichore imbalance from horizontal gene transfer drives the rearrangements to restore balance, or (ii) the rearrangements are a consequence of the host-specific lifestyle. Although recent evidence has refuted the replichore balance hypothesis, there has been no direct evidence for the lifestyle hypothesis. To test this hypothesis, we determined therrnarrangement type for 20Salmonella entericaserovar Typhi strains obtained from human carriers at periodic intervals over multiple years. These strains were also phage typed and analyzed for rearrangements that occurred over long-term storage versus routine culturing. Strains isolated from the same carrier at different time points often exhibited different arrangement types. Furthermore, colonies isolated directly from the Dorset egg slants used to store the strains also had different arrangement types. In contrast, colonies that were repeatedly cultured always had the same arrangement type. Estimated replichore balance of isolated strains did not improve over time, and some of the rearrangements resulted in decreased replicore balance. Our results support the hypothesis that the restricted lifestyle of host-specificSalmonellais responsible for the frequent chromosomal rearrangements in these serovars.IMPORTANCEAlthough it was previously thought that bacterial chromosomes were stable, comparative genomics has demonstrated that bacterial chromosomes are dynamic, undergoing rearrangements that change the order and expression of genes. While mostSalmonellastrains have a conserved chromosomal arrangement type, rearrangements are very common in host-specificSalmonellastrains. This study suggests that chromosome rearrangements in the host-specificSalmonella entericaserovar Typhi, the causal agent of typhoid fever, occur within the human host over time. The results also indicate that rearrangements can occur during long-term maintenance on laboratory medium. Although these genetic changes do not limit survival under slow-growth conditions, they may limit the survival ofSalmonellaTyphi in other environments, as predicted for the role of pseudogenes and genome reduction in niche-restricted bacteria.

Minor shifts towards more natural conditions in captivity improve long-term survival among reintroduced Atlantic salmon

2020 ◽  
Vol 77 (5) ◽  
pp. 931-942
Author(s):  
Andrew B. Harbicht ◽  
Dylan J. Fraser ◽  
William R. Ardren
Keyword(s):  
Atlantic Salmon ◽  
Life Histories ◽  
Thermal Conditions ◽  
Cost Effective ◽  
Growth Conditions ◽  
Adult Survival ◽  
Term Survival ◽  
Long Term Survival ◽  
Release Times

Elevating winter water temperatures is a common practice when rearing salmonids for supplementation or reintroduction. Doing so elevates developmental rates, producing larger juveniles with greater smolt-to-adult survival, but does not guarantee improved adult returns to stocked tributaries. To test whether more natural developmental conditions improve adult returns to stocked tributaries, three consecutive cohorts of yearling (age 1+) landlocked Atlantic salmon (Salmo salar) were released into two tributaries of Lake Champlain. Cohorts were reared under two winter thermal conditions (seasonal surface water and above-seasonal groundwater) and (or) two release times (early and normal). Relative to standard hatchery practices, modelled returns to experimental tributaries increased over replicate cohorts by 286% on average following exposure to seasonal rearing temperatures, but decreased by 89% on average when release dates were advanced. By utilizing cost-effective shifts towards hatchery rearing techniques that more closely resemble natural growth conditions, we demonstrate how hatchery programs may improve long-term survival and returns for fish species with complex life histories involved in supplementation and reintroduction programs.

scholarly journals A Role for Single-Stranded Exonucleases in the Use of DNA as a Nutrient

2009 ◽  
Vol 191 (11) ◽  
pp. 3712-3716 ◽  
Author(s):  
Vyacheslav Palchevskiy ◽  
Steven E. Finkel
Keyword(s):  
Escherichia Coli ◽  
Bacterial Cells ◽  
Wild Type ◽  
Nutrient Source ◽  
Term Survival ◽  
Natural Competence ◽  
E Coli ◽  
Double Stranded Dna ◽  
Better Than

ABSTRACT Nutritional competence is the ability of bacterial cells to utilize exogenous double-stranded DNA molecules as a nutrient source. We previously identified several genes in Escherichia coli that are important for this process and proposed a model, based on models of natural competence and transformation in bacteria, where it is assumed that single-stranded DNA (ssDNA) is degraded following entry into the cytoplasm. Since E. coli has several exonucleases, we determined whether they play a role in the long-term survival and the catabolism of DNA as a nutrient. We show here that mutants lacking either ExoI, ExoVII, ExoX, or RecJ are viable during all phases of the bacterial life cycle yet cannot compete with wild-type cells during long-term stationary-phase incubation. We also show that nuclease mutants, alone or in combination, are defective in DNA catabolism, with the exception of the ExoX− single mutant. The ExoX− mutant consumes double-stranded DNA better than wild-type cells, possibly implying the presence of two pathways in E. coli for the processing of ssDNA as it enters the cytoplasm.

Comparison of the symbiotic and competition phenotypes of Sinorhizobium meliloti PHB synthesis and degradation pathway mutants

2005 ◽  
Vol 51 (7) ◽  
pp. 599-604 ◽  
Author(s):  
P Aneja ◽  
A Zachertowska ◽  
T C Charles
Keyword(s):  
Sinorhizobium Meliloti ◽  
Degradation Pathway ◽  
Nodule Occupancy ◽  
Wild Type ◽  
Term Survival ◽  
Mutant Strains ◽  
Key Factor ◽  
Carbon Excess ◽  
Synthesis And Degradation

The competitive abilities of Sinorhizobium meliloti mutant strains containing lesions in the PHB synthesis (phbC) and degradation (bdhA) pathways were compared. While the bdhA mutant showed no noticeable symbiotic defects on alfalfa host plants when inoculated alone, in mixed inoculation experiments it was found to be less competitive than the wild type for nodule occupancy. Long-term survival of the bdhA mutant on a carbon-limiting medium was not affected. However, when subjected to competition with the wild-type strain in periodic subculturing through alternating carbon-limiting and carbon-excess conditions, the bdhA mutant performed poorly. A more severe defect in competition for growth and nodule occupancy was observed with a mutant unable to synthesize PHB (phbC). These results indicate that the ability to efficiently deposit cellular PHB stores is a key factor influencing competitive survival under conditions of fluctuating nutrient carbon availability, whereas the ability to use these stores is less important.Key words: Sinorhizobium meliloti, PHB metabolism, competition.

scholarly journals Long-Term Survival of Salmonella enterica Serovar Typhimurium Reveals an Infectious State That Is Underrepresented on Laboratory Media Containing Bile Salts

2009 ◽  
Vol 75 (14) ◽  
pp. 4923-4925 ◽  
Author(s):  
Dmitry Apel ◽  
Aaron P. White ◽  
Guntram A. Grassl ◽  
B. Brett Finlay ◽  
Michael G. Surette
Keyword(s):  
Salmonella Enterica ◽  
Bile Salts ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Term Survival ◽  
Long Term Survival ◽  
Selective Media ◽  
Serovar Typhimurium ◽  
Systemic Infections ◽  
Infectious State

ABSTRACT Cells in desiccated Salmonella enterica serovar Typhimurium rdar (red, dry, and rough) morphotype colonies were examined for culturability and infectivity after 30 months. Culturability decreased only 10-fold; however, cells were underrepresented on Salmonella selective media containing bile salts. These cells were mildly attenuated compared to the infectivity of freshly grown cells but still able to cause systemic infections in mice.

scholarly journals Identification of a diacylglycerol acyltransferase gene involved in accumulation of triacylglycerol in Mycobacterium tuberculosis under stress

Microbiology ◽  
2006 ◽  
Vol 152 (9) ◽  
pp. 2717-2725 ◽  
Author(s):  
Tatiana D. Sirakova ◽  
Vinod S. Dubey ◽  
Chirajyoti Deb ◽  
Jaiyanth Daniel ◽  
Tatiana A. Korotkova ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Fatty Acid ◽  
Fatty Acid Synthase ◽  
Growth Conditions ◽  
Diacylglycerol Acyltransferase ◽  
Major Fatty Acid ◽  
Term Survival ◽  
Suitable Target ◽  
Mutant Complementation

Mycobacterium tuberculosis under stress stores triacylglycerol (TG). There are 15 genes in M. tuberculosis that belong to a novel family of TG synthase genes (tgs), but it is not known which of them is responsible for this accumulation of TG. In this paper, it is reported that M. tuberculosis H37Rv accumulated TG under acidic, static or hypoxic growth conditions, or upon treatment with NO, whereas TG accumulation was drastically reduced in the tgs1 (Rv3130c) disrupted mutant. Complementation with tgs1 restored this TG accumulation. C26 was a major fatty acid in this TG, indicating that the TGS1 gene product uses C26 fatty acid, which is known to be produced by the mycobacterial fatty acid synthase. TGS1 expressed in Escherichia coli preferred C26 : 0-CoA for TG synthesis. If TG storage is needed for the long-term survival of M. tuberculosis under dormant conditions, the tgs1 product could be a suitable target for antilatency drugs.

scholarly journals Deletion or Overexpression of Mitochondrial NAD+Carriers inSaccharomyces cerevisiaeAlters Cellular NAD and ATP Contents and Affects Mitochondrial Metabolism and the Rate of Glycolysis

2011 ◽  
Vol 77 (7) ◽  
pp. 2239-2246 ◽  
Author(s):  
Gennaro Agrimi ◽  
Luca Brambilla ◽  
Gianni Frascotti ◽  
Isabella Pisano ◽  
Danilo Porro ◽  
...  
Keyword(s):  
Cellular Metabolism ◽  
Growth Conditions ◽  
Glycolytic Flux ◽  
Energetic Efficiency ◽  
Crabtree Effect ◽  
Wild Type ◽  
Glucose Flux ◽  
Chemostat Cultures ◽  
Biomass Yields

ABSTRACTThe modification of enzyme cofactor concentrations can be used as a method for both studying and engineering metabolism. We variedSaccharomyces cerevisiaemitochondrial NAD levels by altering expression of its specific mitochondrial carriers. Changes in mitochondrial NAD levels affected the overall cellular concentration of this coenzyme and the cellular metabolism. In batch culture, a strain with a severe NAD depletion in mitochondria succeeded in growing, albeit at a low rate, on fully respiratory media. Although the strain increased the efficiency of its oxidative phosphorylation, the ATP concentration was low. Under the same growth conditions, a strain with a mitochondrial NAD concentration higher than that of the wild type similarly displayed a low cellular ATP level, but its growth rate was not affected. In chemostat cultures, when cellular metabolism was fully respiratory, both mutants showed low biomass yields, indicative of impaired energetic efficiency. The two mutants increased their glycolytic fluxes, and as a consequence, the Crabtree effect was triggered at lower dilution rates. Strikingly, the mutants switched from a fully respiratory metabolism to a respirofermentative one at the same specific glucose flux as that of the wild type. This result seems to indicate that the specific glucose uptake rate and/or glycolytic flux should be considered one of the most important independent variables for establishing the long-term Crabtree effect. In cells growing under oxidative conditions, bioenergetic efficiency was affected by both low and high mitochondrial NAD availability, which suggests the existence of a critical mitochondrial NAD concentration in order to achieve optimal mitochondrial functionality.

scholarly journals Long-Term Survival of Campylobacter jejuni at Low Temperatures Is Dependent on Polynucleotide Phosphorylase Activity

2009 ◽  
Vol 75 (23) ◽  
pp. 7310-7318 ◽  
Author(s):  
Nabila Haddad ◽  
Christopher M. Burns ◽  
Jean Michel Bolla ◽  
Hervé Prévost ◽  
Michel Fédérighi ◽  
...  
Keyword(s):  
Campylobacter Jejuni ◽  
Low Temperatures ◽  
Survival Rates ◽  
Polynucleotide Phosphorylase ◽  
Wild Type ◽  
Term Survival ◽  
Poultry Products ◽  
Bacterial Gastroenteritis

ABSTRACT Campylobacter jejuni is a leading cause of bacterial gastroenteritis worldwide. Infection generally occurs after ingestion of contaminated poultry products, usually conserved at low temperatures. The mechanisms promoting survival of C. jejuni in the cold remain poorly understood despite several investigations. The present study provides insight into the survival mechanism by establishing the involvement of polynucleotide phosphorylase (PNPase), a 3′-5′ exoribonuclease with multiple biological functions in cold survival. The role of PNPase was demonstrated genetically using strains with altered pnp genes (which encode PNPase) created in C. jejuni F38011 and C. jejuni 81-76 backgrounds. Survival assays carried out at low temperatures (4 and 10°C) revealed a difference of 3 log CFU/ml between the wild-type and the pnp deletion (Δpnp) strains. This did not result from a general requirement for PNPase because survival rates of the strains were similar at higher growth temperatures (37 or 42°C). trans-Complementation with plasmid pNH04 carrying the pnp gene under the control of its natural promoter restored the cold survival phenotype to the pnp deletion strains (at 4 and 10°C) but not to the same level as the wild type. In this study we demonstrate the role of PNPase in low-temperature survival of C. jejuni and therefore attribute a novel biological function to PNPase directly related to human health.

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