scholarly journals The CiaRH System of Streptococcus pneumoniae Prevents Lysis during Stress Induced by Treatment with Cell Wall Inhibitors and by Mutations in pbp2x Involved in β-Lactam Resistance

2006 ◽  
Vol 188 (5) ◽  
pp. 1959-1968 ◽  
Author(s):  
Thorsten Mascher ◽  
Manuel Heintz ◽  
Dorothea Zähner ◽  
Michelle Merai ◽  
Regine Hakenbeck
Keyword(s):  
Cell Wall ◽  
Streptococcus Pneumoniae ◽  
Growth Phase ◽  
Point Mutations ◽  
Normal Growth ◽  
Stationary Growth Phase ◽  
Clinical Isolates ◽  
Loss Of Function ◽  
Beta Lactam ◽  
Stationary Growth

ABSTRACT The two-component signal-transducing system CiaRH of Streptococcus pneumoniae plays an important role during the development of beta-lactam resistance in laboratory mutants. We show here that a functional CiaRH system is required for survival under many different lysis-inducing conditions. Mutants with an activated CiaRH system were highly resistant to lysis induced by a wide variety of early and late cell wall inhibitors, such as cycloserine, bacitracin, and vancomycin, and were also less susceptible to these drugs. In contrast, loss-of-function CiaRH mutants were hypersusceptible to these drugs and were apparently unable to maintain a stationary growth phase in normal growth medium and under choline deprivation as well. Moreover, disruption of CiaR in penicillin-resistant mutants with an altered pbp2x gene encoding low-affinity PBP2x resulted in severe growth defects and rapid lysis. This phenotype was observed with pbp2x genes containing point mutations selected in the laboratory and with highly altered mosaic pbp2x genes from penicillin-resistant clinical isolates as well. This documents for the first time that PBP2x mutations required for development of beta-lactam resistance are functionally not neutral and are tolerated only in the presence of the CiaRH system. This might explain why cia mutations have not been observed in penicillin-resistant clinical isolates. The results document that the CiaRH system is required for maintenance of the stationary growth phase and for prevention of autolysis triggered under many different conditions, suggesting a major role for this system in ensuring cell wall integrity.

scholarly journals EttA is likely non-essential in Staphylococcus aureus persistence, fitness or resistance to antibiotics

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Michal Meir ◽  
Anna Rozenblit ◽  
Simona Fliger ◽  
Yuval Geffen ◽  
Daniel Barkan
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Growth Phase ◽  
Cell Formation ◽  
Stationary Growth Phase ◽  
Clinical Isolates ◽  
Beta Lactam ◽  
Stationary Growth ◽  
Mechanisms Of Persistence

Abstract Background Tolerance to antibiotics and persistence are associated with antibiotic treatment failures, chronic-relapsing infections, and emerging antibiotic resistance in various bacteria, including Staphylococcus aureus. Mechanisms of persistence are largely unknown, yet have been linked to physiology under low-ATP conditions and the metabolic-inactive state. EttA is an ATP-binding cassette protein, linked in Eschrechia coli to ribosomal hibernation and fitness in stationary growth phase, yet its role in S. aureus physiology is unknown. Results Using whole genome sequencing (WGS) of serial clinical isolates, we identified an EttA-negative S. aureus mutant (ettAstop), and its isogenic wild-type counterpart. We used these two isogenic clones to investigate the role of ettA in S. aureus physiology in starvation and antibiotic stress, and test its role in persistence and antibiotic tolerance. ettAstop and its WT counterpart were similar in their antibiotic resistance profiles to multiple antibiotics. Population dynamics of ettAstop and the WT were similar in low-nutrient setting, with similar recovery from stationary growth phase or starvation. Supra-bacteriocidal concentration of cefazolin had the same killing effect on ettAstop and WT populations, with no difference in persister formation. Conclusions Lack of ettA does not affect S. aureus antibiotic resistance, beta-lactam tolerance, resilience to starvation or fitness following starvation. We conclude the role of ettA in S. aureus physiology is limited or redundant with another, unidentified gene. WGS of serial clinical isolates may enable investigation of other single genes involved in S. aureus virulence, and specifically persister cell formation.

scholarly journals Penicillin-binding proteins 2b and 2x of Streptococcus pneumoniae are primary resistance determinants for different classes of beta-lactam antibiotics.

1996 ◽  
Vol 40 (4) ◽  
pp. 829-834 ◽  
Author(s):  
T Grebe ◽  
R Hakenbeck
Keyword(s):  
Streptococcus Pneumoniae ◽  
Clinical Isolate ◽  
Binding Proteins ◽  
Point Mutations ◽  
Clinical Isolates ◽  
Single Amino Acid ◽  
Beta Lactam ◽  
Penicillin Binding Proteins ◽  
Beta Lactam Antibiotics ◽  
High Level

High-level resistance to beta-lactam antibiotics in Streptococcus pneumoniae is mediated by successive alterations in essential penicillin-binding proteins (PBPs). In the present work, single amino acid changes in S. pneumoniae PBP 2x and PBP 2b that result in reduced affinity for the antibiotic and that confer first-level beta-lactam resistance are defined. Point mutations in the PBP genes were generated by PCR-derived mutagenesis. Those conferring maximal resistance to either cefotaxime (pbp2x) or piperacillin (pbp2b) were obtained after transformation of the susceptible laboratory strain R6 with the PCR-amplified PBP genes and selection on agar with various concentrations of the antibiotic. In the case of PBP 2x, transformants for which the cefotaxime MIC was 0.16 microgram/ml contained the substitution of a Thr for an Ala at position 550 (Thr550-->Ala), close to the PBP homology box Lys547SerGly, a mutation frequently observed in laboratory mutants and in a high-level cefotaxime-resistant clinical isolate as well. After further selection, transformants resisting 0.3 microgram of cefotaxime per ml were obtained; they contained the substitution Gly550 as the result of two mutations in the same codon. In PBP 2b, Thr446-->Ala, adjacent to another homology box Ser443SerAsn, was the mutation selected with piperacillin. This substitution has been described in all clinical isolates with a low-affinity PBP 2b but was distinct from point mutations found in laboratory mutants. Both pbp2b with the single mutation and a mosaic pbp2b of a clinical isolate conferred a twofold increase in piperacillin resistance. Attempts to select PBP 2b variants at higher piperacillin concentrations were unsuccessful. The mutated PBP 2b also markedly reduced the lytic response to piperacillin, suggesting that such a mutation is an important step in resistance development in clinical isolates.

scholarly journals Conversion of Daidzein and Genistein by an Anaerobic Bacterium Newly Isolated from the Mouse Intestine

2008 ◽  
Vol 74 (15) ◽  
pp. 4847-4852 ◽  
Author(s):  
Anastasia Matthies ◽  
Thomas Clavel ◽  
Michael Gütschow ◽  
Wolfram Engst ◽  
Dirk Haller ◽  
...  
Keyword(s):  
Stationary Phase ◽  
Enzyme Induction ◽  
Growth Phase ◽  
Anaerobic Bacterium ◽  
Stationary Growth Phase ◽  
Gut Bacteria ◽  
Soy Isoflavones ◽  
Strictly Anaerobic ◽  
Stationary Growth ◽  
Mouse Intestine

ABSTRACT The metabolism of isoflavones by gut bacteria plays a key role in the availability and bioactivation of these compounds in the intestine. Daidzein and genistein are the most common dietary soy isoflavones. While daidzein conversion yielding equol has been known for some time, the corresponding formation of 5-hydroxy-equol from genistein has not been reported previously. We isolated a strictly anaerobic bacterium (Mt1B8) from the mouse intestine which converted daidzein via dihydrodaidzein to equol as well as genistein via dihydrogenistein to 5-hydroxy-equol. Strain Mt1B8 was a gram-positive, rod-shaped bacterium identified as a member of the Coriobacteriaceae. Strain Mt1B8 also transformed dihydrodaidzein and dihydrogenistein to equol and 5-hydroxy-equol, respectively. The conversion of daidzein, genistein, dihydrodaidzein, and dihydrogenistein in the stationary growth phase depended on preincubation with the corresponding isoflavonoid, indicating enzyme induction. Moreover, dihydrogenistein was transformed even more rapidly in the stationary phase when strain Mt1B8 was grown on either genistein or daidzein. Growing the cells on daidzein also enabled conversion of genistein. This suggests that the same enzymes are involved in the conversion of the two isoflavones.

scholarly journals The extracellular proteome of Rhizobium etli CE3 in exponential and stationary growth phase

2010 ◽  
Vol 8 (1) ◽  
pp. 51 ◽  
Author(s):  
Niurka Meneses ◽  
Guillermo Mendoza-Hernández ◽  
Sergio Encarnación
Keyword(s):  
Growth Phase ◽  
Stationary Growth Phase ◽  
Rhizobium Etli ◽  
Stationary Growth ◽  
Extracellular Proteome

scholarly journals Proteomic Study of the Exponential-Stationary Growth Phase Transition in the Haloarchaea Natrialba magadii and Haloferax volcanii

PROTEOMICS ◽  
2018 ◽  
Vol 18 (14) ◽  
pp. 1800116 ◽  
Author(s):  
Micaela Cerletti ◽  
María Ines Giménez ◽  
Christian Tröetschel ◽  
Celeste D’ Alessandro ◽  
Ansgar Poetsch ◽  
...  
Keyword(s):  
Phase Transition ◽  
Growth Phase ◽  
Stationary Growth Phase ◽  
Haloferax Volcanii ◽  
Stationary Growth ◽  
Proteomic Study ◽  
Natrialba Magadii ◽  
Growth Phase Transition

Effect of Temperature on Growth and Alpha Toxin Production by Clostridium perfringens1

1979 ◽  
Vol 42 (11) ◽  
pp. 848-851 ◽  
Author(s):  
Y. PARK ◽  
E. M. MIKOLAJCIK
Keyword(s):  
Growth Phase ◽  
Incubation Temperature ◽  
Ground Beef ◽  
Population Level ◽  
Toxin Production ◽  
Stationary Growth Phase ◽  
Effect Of Temperature ◽  
Alpha Toxin ◽  
Stationary Growth ◽  
Incubation Temperatures

Growth and alpha toxin production by a strain of Clostridium perfringens was determined in Thioglycollate medium, beef broth with ground beef, and beef broth with ground beef and soy protein. Incubation temperatures ranged from 15 to 50 C. In Thioglycollate medium, maximum alpha toxin production occurred at 35 C and was 40 times greater than that observed at 45 C. However, generation time and maximum population were approximately the same at 35 and 45 C. At 15 C, a two log cycle reduction in viable counts occurred within 6 h. Irrespective of incubation temperature, alpha toxin levels in Thioglycollate medium declined as the incubation period was extended beyond the stationary growth phase. In the beef broth with ground beef system which was studied at 35 C only, the organism grew slower and produced less toxin than in Thioglycollate medium. The amount of alpha toxin detected was influenced to a greater extent by the incubation time and temperature, the holding time beyond the stationary growth phase, and the growth medium than by the population level of C. perfringens.

scholarly journals Various checkpoints prevent the synthesis ofStaphylococcus aureuspeptidoglycan hydrolase LytM in the stationary growth phase

RNA Biology ◽  
2016 ◽  
Vol 13 (4) ◽  
pp. 427-440 ◽  
Author(s):  
Efthimia Lioliou ◽  
Pierre Fechter ◽  
Isabelle Caldelari ◽  
Brian C. Jester ◽  
Sarah Dubrac ◽  
...  
Keyword(s):  
Growth Phase ◽  
Stationary Growth Phase ◽  
Stationary Growth

scholarly journals Poly-β-Hydroxybutyrate Production by the Cyanobacterium Scytonema geitleri Bharadwaja under Varying Environmental Conditions

Biomolecules ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 198 ◽  
Author(s):  
Manoj K. Singh ◽  
Pradeep K. Rai ◽  
Anuradha Rai ◽  
Surendra Singh ◽  
Jay Shankar Singh
Keyword(s):  
Carbon Source ◽  
Growth Phase ◽  
Environmental Conditions ◽  
Carbon Sources ◽  
Stationary Growth Phase ◽  
Stationary Growth ◽  
Cell Weight ◽  
Dry Cell Weight ◽  
Phb Production ◽  
Dry Cell

The production of poly-β-hydroxybutyrate (PHB) under varying environmental conditions (pH, temperature and carbon sources) was examined in the cyanobacterium Scytonema geitleri Bharadwaja isolated from the roof-top of a building. The S. geitleri produced PHB and the production of PHB was linear with the growth of cyanobacterium. The maximum PHB production (7.12% of dry cell weight) was recorded when the cells of S. geitleri were at their stationary growth phase. The production of PHB was optimum at pH 8.5 and 30 °C, and acetate (30 mM) was the preferred carbon source.

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