The Impact of Antibacterial Peptides on Bacterial Lipid Membranes Depends on Stage of Growth

2020 ◽  
Author(s):  
Tzong-Hsien Lee ◽  
Vinzenz Hofferek ◽  
Marc-antoine Sani ◽  
Frances Separovic ◽  
Gavin Reid ◽  
...  
Keyword(s):  
Growth Phase ◽  
Lipid Membranes ◽  
Stationary Growth Phase ◽  
Exponential Growth Phase ◽  
Antibacterial Peptides ◽  
Stationary Growth ◽  
E Coli ◽  
Bacterial Lipid ◽  
Supported Lipid Membranes ◽  
The Impact

The impact of maculatin 1.1 (Mac1) on the mechanical properties of supported lipid membranes derived from exponential growth phase (EGP) and stationary growth phase (SGP) E. coli lipid extracts was...

High Hydrostatic Pressure Come-Up Time and Yeast Viability

1998 ◽  
Vol 61 (12) ◽  
pp. 1657-1660 ◽  
Author(s):  
E. PALOU ◽  
A. LÓPEZ-MALO ◽  
G. V. BARBOSA-CÁNOVAS ◽  
J. WELTI-CHANES ◽  
P. M. DAVIDSON ◽  
...  
Keyword(s):  
Growth Phase ◽  
Growth Cycle ◽  
Stationary Growth Phase ◽  
Yeast Cells ◽  
Exponential Growth Phase ◽  
Stationary Growth ◽  
Survival Fraction ◽  
Zygosaccharomyces Bailii ◽  
Yeast Viability ◽  
Increased Sensitivity

The effects of the come-up time at selected pressures (50 to 689 MPa) on Saccharomyces cerevisiae and Zygosaccharomyces bailii viability were evaluated at 21°C. For Z. bailii the effects of the water activity (aw) of the suspension media and the stage of the growth cycle were also investigated. Pressure come-up times exerted an important effect on the yeast survival fraction, decreasing counts as pressure increased. An increased sensitivity to pressure treatments was observed with yeast cells from the exponential growth phase. Lethality increased as aw of the suspension media increased. For an aw of 0.98 and cells from the stationary growth phase, pressure treatments at less than 200 MPa had no effect on Z. bailii viability; however, no survivors (<10 CFU/ml) were observed in treatments applied only for the time needed to reach pressures greater than 517 MPa. Yeast survivor curves showed an excellent fit (r > 0.996) when described by a phenomenological model based on the Fermi equation, S(P) = 1/|1 + exp[(P − Pc)/k]|, where S(P) is the survival fraction, P is the pressure, Pc is a critical pressure corresponding to 50% survival, and k is a constant representing the steepness of the curve.

Effect of bacterial growth stage on resistance to chlorine disinfection

2011 ◽  
Vol 64 (1) ◽  
pp. 7-13 ◽  
Author(s):  
C. Cherchi ◽  
A. Z. Gu
Keyword(s):  
Escherichia Coli ◽  
Growth Phase ◽  
Growth Stage ◽  
Exponential Growth Phase ◽  
Lag Phase ◽  
Growth Phases ◽  
Bacterial Strains ◽  
E Coli ◽  
Chlorine Disinfection ◽  
The Impact

The mechanisms and factors that affect microbial resistance to chlorine disinfection have not been fully elucidated. In this study, we investigated the impact of the cell growth stage on chlorine disinfection efficiency. Specifically, we evaluated the impact of the growth stage on chlorination resistance by comparing the inactivation efficiencies of two indicator bacterial strains (Escherichia coli K12 and Escherichia coli 0157:H7) obtained from various growth phases, using Chick-Watson kinetic parameters. For both E. coli strains (K12 and 0157:H7), the inactivation rate constants are the lowest at stationary phase (0.19 and 0.32) compared to those at initial lag (0.54 and 0.76) and exponential growth phase (0.63 and 0.69), respectively. These results suggested that the abundance of resistant subpopulations increases at stressed stationary conditions and E. coli cells obtained from the stationary growth phase exhibited more resistance and lower inactivation efficiency compared to those from the lag and exponential phases. This implies that microbes in wastewater treatment process with varying solids retention times (SRTs, which indicate growth rates) may show different extents of chlorine resistance. Comparison of the coefficient of dilution (n) values in both E. coli strains for the various growth phases suggest that cells seem to be more sensitive to disinfectant concentration at the stationary-lag phase than that at the exponential stage. Comparing the two E. coli strains, higher inactivation rates were observed for the pathogenic O157:H7 than for K12 at different stages of growth. The strain-to-strain variability in survivability to chlorine exposure has to be considered when selecting indicator microorganisms for water quality monitoring.

Isolation and characterization of thermophilic bacteria capable of lysing microbial cells in activated sludge

2006 ◽  
Vol 54 (9) ◽  
pp. 35-43 ◽  
Author(s):  
Yu-Dong Song ◽  
Hong-Ying Hu
Keyword(s):  
Activated Sludge ◽  
Growth Phase ◽  
Thermophilic Bacteria ◽  
Great Influence ◽  
Stationary Growth Phase ◽  
Lytic Activity ◽  
Stationary Growth ◽  
E Coli ◽  
Isolation And Characterization ◽  
Culture Supernatants

To find an efficient biological method to solubilize waste activated sludge (WAS) from the biological wastewater treatment process, several strains of thermophilic bacteria capable of solubilizing WAS were isolated from sewage sludge compost. The culture supernatants of the isolates were able to lyse vegetable bacterial cells and the lytic activity mainly came from the exoenzyme produced by the isolates. The culture supernatants of the different isolates showed different lysis characteristics. The factors affecting bacterial cell lysis were investigated using E. coli as a model bacterium. The E. coli cells were lysed easily at higher temperature (60 °C or 70 °C) while little lytic activity by the supernatants of isolates was observed at lower temperature (50 °C). The level of pH also had great influence on the lysis of E. coli cells. The E. coli cells in the early stationary growth phase were easier to lyse than those in the late stationary growth phase or death phase.

scholarly journals Analysis of cell-growth-phase-related variations in hyaluronate synthase activity of isolated plasma-membrane fractions of cultured human skin fibroblasts

1986 ◽  
Vol 237 (2) ◽  
pp. 333-342 ◽  
Author(s):  
N Mian
Keyword(s):  
Plasma Membrane ◽  
Growth Phase ◽  
Plasma Membranes ◽  
Glucuronic Acid ◽  
Stationary Growth Phase ◽  
Binding Activity ◽  
Exponential Growth Phase ◽  
Human Skin Fibroblasts ◽  
Stationary Growth ◽  
Hyaluronate Synthase

Hyaluronate synthase activity is localized exclusively in plasma-membrane fractions of cultured human skin fibroblasts. The enzyme activity of plasma membranes prepared from exponential-growth-phase cells was about 6.5 times that of stationary-growth-phase cells. Hyaluronate synthase from exponential-growth-phase cells exhibited lower Km and higher Vmax. values for both UDP-N-acetylglucosamine and UDP-glucuronic acid and higher rate of elongation of hyaluronate chains compared with the enzyme from stationary-growth-phase cells. Hyaluronate synthase exhibited an extremely short half-life, 2.2 h and 3.8 h respectively when cells were treated with cycloheximide and actinomycin D. The cell-growth-phase-dependent variations in hyaluronate synthase activity appear to be due to its high turnover rate as well as due to some post-translational modification of the enzyme protein as cells progress from early exponential to stationary growth phase. The isolated plasma membranes contained a protein (Mr approx. 450,000) that was selectively autophosphorylated from [gamma-32P]ATP in vitro in the presence of hyaluronate precursors in the reaction mixture and that also exhibited some hyaluronate-synthesis-related properties. The 32P-labelled protein isolated from plasma membranes of exponentially growing cells expressed an efficient UDP-[14C]glucuronic acid- and UDP-N-acetyl[3H]glucosamine-binding activity and was able to synthesize oligosaccharides (Mr 5000) of [14C]glucuronic acid and N-acetyl[3H]glucosamine residues. The corresponding protein of stationary-growth-phase cells, which expressed much higher nucleotide-sugar-precursor-binding activity, appeared to have lost its oligosaccharide-synthesizing activity.

Construction of a [NiFe]-hydrogenase deletion mutant of Desulfovibrio vulgaris Hildenborough

2005 ◽  
Vol 33 (1) ◽  
pp. 59-60 ◽  
Author(s):  
A. Goenka ◽  
J.K. Voordouw ◽  
W. Lubitz ◽  
W. Gärtner ◽  
G. Voordouw
Keyword(s):  
Growth Phase ◽  
Exponential Growth ◽  
Deletion Mutant ◽  
Stationary Growth Phase ◽  
Exponential Growth Phase ◽  
Desulfovibrio Vulgaris ◽  
Wild Type ◽  
Stationary Growth ◽  
Desulfovibrio Vulgaris Hildenborough ◽  
Mutant Cells

A mutant of Desulfovibrio vulgaris Hildenborough lacking a gene for [NiFe] hydrogenase was generated. Growth studies, performed for the mutant in comparison with the wild-type, showed no strong differences during the exponential growth phase. However, the mutant cells died more rapidly in the stationary growth phase.

scholarly journals Temporal Expression of the Bacillus subtilis secAGene, Encoding a Central Component of the Preprotein Translocase

1999 ◽  
Vol 181 (2) ◽  
pp. 493-500 ◽  
Author(s):  
Markus Herbort ◽  
Michael Klein ◽  
Erik H. Manting ◽  
Arnold J. M. Driessen ◽  
Roland Freudl
Keyword(s):  
Bacillus Subtilis ◽  
Growth Phase ◽  
Exponential Growth ◽  
De Novo ◽  
Stationary Growth Phase ◽  
Extracellular Proteins ◽  
Exponential Growth Phase ◽  
Central Component ◽  
Temporal Expression ◽  
Stationary Growth

ABSTRACT In Bacillus subtilis, the secretion of extracellular proteins strongly increases upon transition from exponential growth to the stationary growth phase. It is not known whether the amounts of some or all components of the protein translocation apparatus are concomitantly increased in relation to the increased export activity. In this study, we analyzed the transcriptional organization and temporal expression of the secA gene, encoding a central component of the B. subtilis preprotein translocase. We found that secA and the downstream gene (prfB) constitute an operon that is transcribed from a vegetative (ςA-dependent) promoter located upstream ofsecA. Furthermore, using different independent methods, we found that secA expression occurred mainly in the exponential growth phase, reaching a maximal value almost precisely at the transition from exponential growth to the stationary growth phase. Following to this maximum, the de novo transcription ofsecA sharply decreased to a low basal level. Since at the time of maximal secA transcription the secretion activity of B. subtilis strongly increases, our results clearly demonstrate that the expression of at least one of the central components of the B. subtilis protein export apparatus is adapted to the increased demand for protein secretion. Possible mechanistic consequences are discussed.

scholarly journals Model-based Characterization of the Parameters of Dissimilatory Sulfate Reduction Under the Effect of Different Initial Density of Desulfovibrio piger Vib-7 Bacterial Cells

2015 ◽  
Vol 9 (1) ◽  
pp. 55-69 ◽  
Author(s):  
Ivan Kushkevych ◽  
Marco Bolis ◽  
Milan Bartos
Keyword(s):  
Sulfate Reduction ◽  
Bacterial Growth ◽  
Growth Phase ◽  
Initial Density ◽  
Stationary Growth Phase ◽  
Exponential Growth Phase ◽  
Dissimilatory Sulfate Reduction ◽  
Bacterial Cells ◽  
Stationary Growth ◽  
Initial Concentration

The objective of this study was to design a model of dissimilatory sulfate reduction process using the Verhulst function, with a particular focus on the kinetics of bacterial growth, sulfate and lactate consumption, and accumulation of hydrogen sulfide and acetate. The effect of the initial density (0.12±0.011, 0.25±0.024, 0.5±0.048 and 1.0±0.096 mg cells/ml of medium) of the sulfate-reducing bacteriaDesulfovibrio pigerVib-7 on the growth and dissimilatory sulfate reduction was studied. The exponential growth phase of theD. pigerVib-7 was observed for 72 hours of cultivation at the (0.12 and 0.25 mg/ml) initial concentration of bacterial cells. Sulfate and lactate were consumed incompletely during this time. The increase in the initial concentration of cells to 0.5 and 1 mg/ml led to a shortening of the exponential bacterial growth phase and a shift to the stationary phase of the growth. In the case of 0.5 mg/ml seeding, the stationary growth phase was observed in the 36thhour of cultivation. The increase in the initial concentration of cells to 1 mg/ml led to the beginning of the stationary growth phase in 24th hours of cultivation. Under these conditions, sulfate and lactate were consumed completely in the 48th hour of cultivation. The kinetic analysis of the curves of bacterial growth and the process of dissimilatory sulfate reduction byD. pigerVib-7 was carried out.

scholarly journals Azithromycin Exhibits Bactericidal Effects on Pseudomonas aeruginosa through Interaction with the Outer Membrane

2005 ◽  
Vol 49 (4) ◽  
pp. 1377-1380 ◽  
Author(s):  
Yoshifumi Imamura ◽  
Yasuhito Higashiyama ◽  
Kazunori Tomono ◽  
Koichi Izumikawa ◽  
Katsunori Yanagihara ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Outer Membrane ◽  
Growth Phase ◽  
Exponential Growth ◽  
Divalent Cations ◽  
Stationary Growth Phase ◽  
Exponential Growth Phase ◽  
Stationary Growth ◽  
Outer Membranes ◽  
Bactericidal Effects

ABSTRACT The aim of the present study was to elucidate the effect of the macrolide antibiotic azithromycin on Pseudomonas aeruginosa. We studied the susceptibility to azithromycin in P. aeruginosa PAO1 using a killing assay. PAO1 cells at the exponential growth phase were resistant to azithromycin. In contrast, PAO1 cells at the stationary growth phase were sensitive to azithromycin. The divalent cations Mg2+ and Ca2+ inhibited this activity, suggesting that the action of azithromycin is mediated by interaction with the outer membranes of the cells, since the divalent cations exist between adjacent lipopolysaccharides (LPSs) and stabilize the outer membrane. The divalent cation chelator EDTA behaved in a manner resembling that of azithromycin; EDTA killed more PAO1 in the stationary growth phase than in the exponential growth phase. A 1-N-phenylnaphthylamine assay showed that azithromycin interacted with the outer membrane of P. aeruginosa PAO1 and increased its permeability while Mg2+ and Ca2+ antagonized this action. Our results indicate that azithromycin directly interacts with the outer membrane of P. aeruginosa PAO1 by displacement of divalent cations from their binding sites on LPS. This action explains, at least in part, the effectiveness of sub-MICs of macrolide antibiotics in pseudomonal chronic airway infection.

scholarly journals Surface of Lactic Acid Bacteria: Relationships between Chemical Composition and Physicochemical Properties

2000 ◽  
Vol 66 (6) ◽  
pp. 2548-2554 ◽  
Author(s):  
Christophe J. P. Boonaert ◽  
Paul G. Rouxhet
Keyword(s):  
Lactic Acid ◽  
Chemical Composition ◽  
Lactic Acid Bacteria ◽  
Physicochemical Properties ◽  
Growth Phase ◽  
Surface Composition ◽  
Stationary Growth Phase ◽  
Contact Angles ◽  
Exponential Growth Phase ◽  
Stationary Growth

ABSTRACT The surface chemical composition and physicochemical properties (hydrophobicity and zeta potential) of two lactic acid bacteria,Lactococcus lactis subsp. lactis bv. diacetilactis and Lactobacillus helveticus, have been investigated using cells harvested in exponential or stationary growth phase. The surface composition determined by X-ray photoelectron spectroscopy (XPS) was converted into a molecular composition in terms of proteins, polysaccharides, and hydrocarbonlike compounds. The concentration of the last was always below 15% (wt/wt), which is related to the hydrophilic character revealed by water contact angles of less than 30°. The surfaces of L. lactis cells had a polysaccharide concentration about twice that of proteins. The S-layer of L. helveticus was either interrupted or crossed by polysaccharide-rich compounds; the concentration of the latter was higher in the stationary growth phase than in the exponential growth phase. Further progress was made in the interpretation of XPS data in terms of chemical functions by showing that the oxygen component at 531.2 eV contains a contribution of phosphate in addition to the main contribution of the peptide link. The isoelectric points were around 2 and 3, and the electrophoretic mobilities above pH 5 (ionic strength, 1 mM) were about −3.0 × 10−8 and −0.6 × 10−8 m2 s−1 V−1 forL. lactis and L. helveticus, respectively. The electrokinetic properties of the latter reveal the influence of carboxyl groups, while the difference between the two strains is related to a difference between N/P surface concentration ratios, reflecting the relative exposure of proteins and phosphate groups at the surface.

Some physiological characteristics of a phosphate-removing bacterium, microlunatus phosphovorus, and a simplified isolation and identification method for phosphate-removing bacteria

1998 ◽  
Vol 38 (1) ◽  
pp. 149-157 ◽  
Author(s):  
Y. Ubukata ◽  
S. Takii
Keyword(s):  
Growth Phase ◽  
Stationary Growth Phase ◽  
Physiological Characteristics ◽  
Exponential Growth Phase ◽  
Bacterial Cells ◽  
Stationary Growth ◽  
Isolation And Identification ◽  
Identification Method ◽  
Energy Storage Material ◽  
Aerobic And Anaerobic

Some physiological characteristics of a phosphate (Pi)-removing bacterium, Microlunatus phosphovorus, are investigated using aerobically grown cells and cells exhibiting excess Pi accumulation (EPA) in order to determine a simplified isolation and identification method for other Pi-removing bacteria. Such a method would save on the amount of sterile equipment needed, and reduce the number of experimental steps and labor time. The EPA activity of the isolate reached a plateau 13 hours into the anaerobic incubation time, but it reached 70% of that level after only 5 hours. The EPA activity of the cells during the stationary growth phase was higher than that during the exponential growth phase. Polyphosphate (polyP) accumulated in the cells was shown to be used as an energy storage material (a phosphagen) under both aerobic and anaerobic conditions. During aerobic starvation, the rate of decrease in the ATP concentration of the suspension of cells that contained polyP was markedly less than that of the suspension of cells without polyP. Therefore, bacterial cells rich in polyP survive longer than bacterial cells lacking polyP.

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