Experimental Examination of Bacteriophage
Latent-Period Evolution as a Response to Bacterial
Availability

ABSTRACT For obligately lytic bacteriophage (phage) a trade-off exists between fecundity (burst size) and latent period (a component of generation time). This trade-off occurs because release of phage progeny from infected bacteria coincides with destruction of the machinery necessary to produce more phage progeny. Here we employ phage mutants to explore issues of phage latent-period evolution as a function of the density of phage-susceptible bacteria. Theory suggests that higher bacterial densities should select for shorter phage latent periods. Consistently, we have found that higher host densities (≥∼107 bacteria/ml) can enrich stocks of phage RB69 for variants that display shorter latent periods than the wild type. One such variant, dubbed sta5, displays a latent period that is ∼70 to 80% of that of the wild type—which is nearly as short as the RB69 eclipse period—and which has a corresponding burst size that is ∼30% of that of the wild type. We show that at higher host densities (≥∼107 bacteria/ml) the sta5 phage can outcompete the RB69 wild type, though only under conditions of direct (same-culture) competition. We interpret this advantage as corresponding to slightly faster sta5 population growth, resulting in multifold increases in mutant frequency during same-culture growth. The sta5 advantage is lost, however, given indirect (different-culture) competition between the wild type and mutant or given same-culture competition but at lower densities of phage-susceptible bacteria (≤∼106 bacteria/ml). From these observations we suggest that phage displaying very short latent periods may be viewed as specialists for propagation when bacteria within cultures are highly prevalent and transmission between cultures is easily accomplished.

Download Full-text

Characterization of E coli phage isolated from sewage

Al-Qadisiyah Journal of Veterinary Medicine Sciences ◽

10.29079/vol9iss2art110 ◽

2010 ◽

Vol 9 (2) ◽

pp. 45 ◽

Cited By ~ 2

Author(s):

G.A. Al-Mola, and I. H. Al-Yassari

Keyword(s):

Statistical Analysis ◽

Latent Period ◽

Burst Size ◽

Host Cells ◽

Effect Of Temperature ◽

Lytic Bacteriophage ◽

Bacterial Cells ◽

Dilution Factor ◽

Countable Number ◽

Phage Titre

Bacteriophage are viruses that infect bacterial cells. as with all viruses, phage are nonliving agents and thus require the use of the host‟s metabolic processes to replicate itself. in this study, the phage of interest are those that infect and lyses E. colt host cells. when phage are released from the ruptured host, distinct zones of clearing (plaques) form. the original E. colt host cells for this experiment came from a sample of raw sewage. in order to obtain the bacteriophage, a procedure of enrichment, isolation, dilution and seeding was followed, the presence of distinct plaques indicated that lytic bacteriophage had been successfully amplified, separated and grown.This study included determination of phage titre, latent period , rise period and the burst size of the phage and effect some of factor on phage titre such as (temperature, ether and chloroform) .for determination ofhage titre used series of dilutions(10-1, 10-2, 10-3, 10-4, 10-4, 10-6, 10-7, 10-8, 10-9) the dilution factor gave the best countable number of plaques is(103). this dilution factor was then used for all other experiments, the latent period , rise period and the burst size of the phage are determined by countable number of plaques and phage titre(titer: plaque-forming unit(p.f.u) during 10,20,30,40,50, and 60 minutes . it was (4.7x105 „ 5.3x105 and 6.0x105)during 1O,20and30minutes respectively in the latent period ,but it was (8.5x105 8.9x10‟ 9.3x105)during 40,50,and 60 minutes respectively in the rise period .then the burst size of the phage is counted by the ratio of the phage titer after rise period to that during the latent period it was(1.67).This study also included effect of temperature on phage titre the statistical analysis was significantly increase P<0.05 in phage titre at the temperature37 C° comparing with phage titre at the temperature 50 C° and phage titre at the temperature 65 C°. effects of ether and chloroform on number of plaques and phage titre during 5,10,15 ,20,25 ,30,35 and 40 minutes it was(0.7x105 , 0.3x105 , 0 , 0 , 0 , 0, 0 and 0) respectively in ether sensitivity, but the phage titre in chloroform sensitivity was completely inactivated by chloroform treatment, the statistical analysis (freedom degree ( 2,21 ) and F value=52.60 was high] significant increase (P<0.05) in phage titre in normal saline comparing with phage titre in ether and chloroform sensitivity

Download Full-text

Bacteriophage T4 resistance to lysis-inhibition collapse

Genetics Research ◽

10.1017/s0016672399003833 ◽

1999 ◽

Vol 74 (1) ◽

pp. 1-11 ◽

Cited By ~ 32

Author(s):

STEPHEN T. ABEDON

Keyword(s):

Latent Period ◽

Burst Size ◽

Bacteriophage T4 ◽

Size Increase ◽

Wild Type ◽

Lysis Inhibition ◽

T4 Bacteriophage ◽

Infected Cells

Lysis inhibition is a mechanism of latent-period extension and burst-size increase that is induced by the T4 bacteriophage adsorption of T4-infected cells. Mutants of T4 genes imm, sp and 5 (specifically the ts1 mutant of 5) display some lysis inhibition. However, these mutants experience lysis-inhibition collapse, the lysis of lysis-inhibited cells, earlier than wild-type-infected cells (i.e. their collapse occurs prematurely). Lysis from without is a lysis induced by excessive T4 adsorption. Gp5 is an inducer of lysis from without while gpimm and gpsp effect resistance to lysis from without. This paper shows that interfering with the adsorption of phages to imm-, sp- or 5ts1-mutant-infected cells, in a variety of contexts, inhibits premature lysis-inhibition collapse. From these data it is inferred that wild-type T4-infected cells display resistance to lysis-inhibition collapse by a mechanism resembling resistance to lysis from without.

Download Full-text

On measuring selection in experimental evolution

Biology Letters ◽

10.1098/rsbl.2010.0580 ◽

2010 ◽

Vol 7 (2) ◽

pp. 210-213 ◽

Cited By ~ 97

Author(s):

Luis-Miguel Chevin

Keyword(s):

Growth Rate ◽

Population Growth ◽

Growth Rates ◽

Experimental Evolution ◽

Generation Time ◽

Evolutionary Biology ◽

Wild Type ◽

Vast Array ◽

Fitness Effects ◽

Accurate Comparison

Distributions of mutation fitness effects from evolution experiments are available in an increasing number of species, opening the way for a vast array of applications in evolutionary biology. However, comparison of estimated distributions among studies is hampered by inconsistencies in the definitions of fitness effects and selection coefficients. In particular, the use of ratios of Malthusian growth rates as ‘relative fitnesses’ leads to wrong inference of the strength of selection. Scaling Malthusian fitness by the generation time may help overcome this shortcoming, and allow accurate comparison of selection coefficients across species. For species reproducing by binary fission (neglecting cellular death), ln2 can be used as a correction factor, but in general, the growth rate and generation time of the wild-type should be provided in studies reporting distribution of mutation fitness effects. I also discuss how density and frequency dependence of population growth affect selection and its measurement in evolution experiments.

Download Full-text

TSP, a virulent Podovirus can control the growth of Staphylococcus aureus till 12 hours

10.21203/rs.3.rs-170860/v1 ◽

2021 ◽

Author(s):

Rabia Tabassum ◽

Iqbal Ahmed Alvi ◽

Muhammad Asif ◽

Abdul Basit ◽

Shafiq ur Rehman

Keyword(s):

Staphylococcus Aureus ◽

Latent Period ◽

Genome Sequence ◽

Burst Size ◽

Gc Content ◽

Comparative Genomic ◽

Broad Host Range ◽

Lytic Bacteriophage ◽

Short Latent Period ◽

Promising Therapeutic Approach

Abstract Methicillin-resistant Staphylococcus aureus (MRSA) is a prevailing nosocomial pathogen that causes a large number of diseases in healthcare and community settings. The MRSA causes infections in different tissues of immunocompromised individuals leading to increased morbidity and mortality. It possess various virulence mechanisms to show resistance against to a lot of beta-lactam antibiotics. To tackle this emerging issue of MRSA, there is an urgent need of antibiotic alternatives and utilizing lytic bacteriophages is one of the best promising therapeutic approach. In the present study, a lytic bacteriophage TSP was isolated from hospital wastewater against MRSA. Its morphology, physiology, host specificity, burst size and lytic spectrum were determined and complete genome sequence was analyzed. TSP phage efficiently inhibit bacterial growth for up to 12 hours. TSP phage showed broad lytic spectrum against clinical isolates of MRSA (78%) and MSSA (37%). It showed stability at varying temperatures (25ºC, 37ºC) and pH (5–9), while its maximum storage stability was observed at 4ºC. It had short latent period (20min) and high burst size (103 PFU/ infected cell). TSP genome sequence and restriction analysis revealed that its genome is linear having 17,987 bp in length with an average GC content of 29.7%. The TSP genome showed 98% similarity to S aureus phages SCH1, SCH11 and vB SauP-436A1. According to comparative genomic analysis and phylogenetic tree analysis, TSP phage can be considered as a member of genus “P68viruses”. The strong lytic activity, broad host range and short latent period along with absence of any lysogenic and toxic genes make TSP a very good candidate for phage therapy against MRSA infections if prove safe during in vivo studies.

Download Full-text

Isolation and properties of a bacteriophage lytic for a wide range of pseudomonads

Canadian Journal of Microbiology ◽

10.1139/m71-109 ◽

1971 ◽

Vol 17 (5) ◽

pp. 677-682 ◽

Cited By ~ 18

Author(s):

R. A. Kelln ◽

R. A. J. Warren

Keyword(s):

Latent Period ◽

Pseudomonas Fluorescens ◽

Host Range ◽

Burst Size ◽

Broad Host Range ◽

Lytic Bacteriophage ◽

Bacterial Strains ◽

Short Tail ◽

Wide Range ◽

Different Strains

The lytic bacteriophage ø-S1 was isolated from sewage using a strain of Pseudomonas fluorescens as host. It had a hexagonal head 60 nm in diameter and a short tail 30 nm long. ø-S1 had a broad host range, lysing strains from 10 biotypes of Pseudomonads. Although the latent period was fairly constant for the bacterial strains tested, the burst size varied considerably. The rate of adsorption of the phage to different strains also varied considerably.

Download Full-text

Evaluation of the Efficacy of a Bacteriophage in the Treatment of Pneumonia Induced by Multidrug ResistanceKlebsiella pneumoniaein Mice

BioMed Research International ◽

10.1155/2015/752930 ◽

2015 ◽

Vol 2015 ◽

pp. 1-9 ◽

Cited By ~ 41

Author(s):

Fang Cao ◽

Xitao Wang ◽

Linhui Wang ◽

Zhen Li ◽

Jian Che ◽

...

Keyword(s):

Bacterial Infections ◽

Burst Size ◽

Multidrug Resistant ◽

Lung Lesion ◽

Lytic Bacteriophage ◽

Short Latent Period ◽

Dose Dependent ◽

Antibiotic Control

Multidrug-resistantKlebsiella pneumoniae(MRKP) has steadily grown beyond antibiotic control. However, a bacteriophage is considered to be a potential antibiotic alternative for treating bacterial infections. In this study, a lytic bacteriophage, phage 1513, was isolated using a clinical MRKP isolate KP 1513 as the host and was characterized. It produced a clear plaque with a halo and was classified as Siphoviridae. It had a short latent period of 30 min, a burst size of 264 and could inhibit KP 1513 growthin vitrowith a dose-dependent pattern. Intranasal administration of a single dose of 2 × 109 PFU/mouse 2 h after KP 1513 inoculation was able to protect mice against lethal pneumonia. In a sublethal pneumonia model, phage-treated mice exhibited a lower level ofK. pneumoniaeburden in the lungs as compared to the untreated control. These mice lost less body weight and exhibited lower levels of inflammatory cytokines in their lungs. Lung lesion conditions were obviously improved by phage therapy. Therefore, phage 1513 has a great effectin vitroandin vivo, which has potential to be used as an alternative to an antibiotic treatment of pneumonia that is caused by the multidrug-resistantK. pneumoniae.

Download Full-text

LATENT PERIOD AND GENERATION TIME FOR TWO PLANT VIRUSES

American Journal of Botany ◽

10.1002/j.1537-2197.1952.tb13075.x ◽

1952 ◽

Vol 39 (9) ◽

pp. 613-618 ◽

Cited By ~ 5

Author(s):

C. E. Yarwood

Keyword(s):

Latent Period ◽

Generation Time ◽

Plant Viruses

Download Full-text

Emergent multicellular life cycles in filamentous bacteria owing to density-dependent population dynamics

Journal of The Royal Society Interface ◽

10.1098/rsif.2011.0102 ◽

2011 ◽

Vol 8 (65) ◽

pp. 1772-1784 ◽

Cited By ~ 19

Author(s):

Valentina Rossetti ◽

Manuela Filippini ◽

Miroslav Svercel ◽

A. D. Barbour ◽

Homayoun C. Bagheri

Keyword(s):

Cell Division ◽

Population Growth ◽

Generation Time ◽

Single Cells ◽

Bacterial Species ◽

Life Forms ◽

Life Cycles ◽

Morphological Properties ◽

Filamentous Bacteria ◽

Growth Phases

Filamentous bacteria are the oldest and simplest known multicellular life forms. By using computer simulations and experiments that address cell division in a filamentous context, we investigate some of the ecological factors that can lead to the emergence of a multicellular life cycle in filamentous life forms. The model predicts that if cell division and death rates are dependent on the density of cells in a population, a predictable cycle between short and long filament lengths is produced. During exponential growth, there will be a predominance of multicellular filaments, while at carrying capacity, the population converges to a predominance of short filaments and single cells. Model predictions are experimentally tested and confirmed in cultures of heterotrophic and phototrophic bacterial species. Furthermore, by developing a formulation of generation time in bacterial populations, it is shown that changes in generation time can alter length distributions. The theory predicts that given the same population growth curve and fitness, species with longer generation times have longer filaments during comparable population growth phases. Characterization of the environmental dependence of morphological properties such as length, and the number of cells per filament, helps in understanding the pre-existing conditions for the evolution of developmental cycles in simple multicellular organisms. Moreover, the theoretical prediction that strains with the same fitness can exhibit different lengths at comparable growth phases has important implications. It demonstrates that differences in fitness attributed to morphology are not the sole explanation for the evolution of life cycles dominated by multicellularity.

Download Full-text