scholarly journals Population cycles and species diversity in dynamic Kill-the-Winner model of microbial ecosystems

2016 ◽  
Author(s):  
Sergei Maslov ◽  
Kim Sneppen
Keyword(s):  
Species Diversity ◽  
Bacterial Population ◽  
Population Cycles ◽  
Volterra Equations ◽  
Bacterial Populations ◽  
Microbial Ecosystems ◽  
Dynamic Scenario ◽  
Cyclic Dynamics ◽  
Ecosystem Diversity ◽  
Static Equilibrium State

AbstractDeterminants of species diversity in microbial ecosystems remain poorly understood. Bacteriophages are believed to increase the diversity by the virtue of Kill-the-Winner infection bias preventing the fastest growing organism from taking over the community. Phage-bacterial ecosystems are traditionally described in terms of the static equilibrium state of Lotka-Volterra equations in which bacterial growth is exactly balanced by losses due to phage predation. Here we consider a more dynamic scenario in which phage infections give rise to abrupt and severe collapses of bacterial populations whenever they become sufficiently large. As a consequence, each bacterial population in our model follows cyclic dynamics of exponential growth interrupted by sudden declines. The total population of all species fluctuates around the carrying capacity of the environment, making these cycles cryptic. While a subset of the slowest growing species in our model is always driven towards extinction, in general the overall ecosystem diversity remains high. The number of surviving species is inversely proportional to the variation in their growth rates but increases with the frequency and severity of phage-induced collapses. Thus counter-intuitively we predict that microbial communities exposed to more violent perturbations should have higher diversity.

scholarly journals Population cycles and species diversity in dynamic Kill-the-Winner model of microbial ecosystems

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Sergei Maslov ◽  
Kim Sneppen
Keyword(s):  
Species Diversity ◽  
Population Cycles ◽  
Microbial Ecosystems

COUNTING TOTAL BACTERIA IN LAND ORGANIC WASTE HOUSEHOLD AND LAND INORGANIC WITH TOTAL PLATE COUNT METHOD (TPC)

2017 ◽  
Vol 4 (2) ◽  
pp. 87-91
Author(s):  
Ekamaida Ekamaida
Keyword(s):  
Soil Fertility ◽  
Bacterial Population ◽  
Organic Soil ◽  
Biological Properties ◽  
Plate Count ◽  
Bacterial Populations ◽  
Fertility Data ◽  
Plate Count Method ◽  
The Mean ◽  
Total Bacteria

The soil fertility aspect is characterized by the good biological properties of the soil. One important element of the soil biological properties is the bacterial population present in it. This research was conducted in the laboratory of Microbiology University of Malikussaleh in the May until June 2016. This study aims to determine the number of bacterial populations in soil organic and inorganic so that can be used as an indicator to know the level of soil fertility. Data analysis was done by T-Test that is by comparing the mean of observation parameter to each soil sample. The sampling method used is a composite method, which combines 9 of soil samples taken from 9 sample points on the same plot diagonally both on organic soil and inorganic soil. The results showed the highest bacterial population was found in total organic soil cfu 180500000 and total inorganic soil cfu 62.500.000

Seasonal variations in heterotrophic bacterial populations in waters off Sydney

1964 ◽  
Vol 15 (1) ◽  
pp. 73
Author(s):  
AD Brown
Keyword(s):  
Negative Correlation ◽  
Seasonal Variations ◽  
Bacterial Population ◽  
Heterotrophic Bacteria ◽  
Bacterial Count ◽  
Early Summer ◽  
Total Bacterial Count ◽  
Bacterial Populations ◽  
Seawater Samples

Viable counts were made of heterotrophic bacteria in seawater samples taken from 0, 25, 50, 75, and 100 m at one station off Sydney over a period of 2 years. Populations, which fell largely within the range of 10-1000/ml, tended to be higher in spring and early summer than at other times. Some evidence was obtained of a negative correlation between bacterial population and chlorinity. There was no evidence of a correlation between bacterial populations and several other variables which were examined. A (presumed) species of Chromobacterium occurred intermittently at the lower depths with some suggestion of a correlation with season and total bacterial count.

Antimicrobial Effects of Trisodium Phosphate Against Bacteria Attached to Beef Tissue

1994 ◽  
Vol 57 (11) ◽  
pp. 952-955 ◽  
Author(s):  
J. S. DICKSON ◽  
C. G. NETTLES CUTTER ◽  
G. R. SIRAGUSA
Keyword(s):  
Adipose Tissue ◽  
Bacterial Population ◽  
Model System ◽  
Trisodium Phosphate ◽  
Phosphate Solution ◽  
Escherichia Coli O157 ◽  
Lean Tissue ◽  
Bacterial Populations ◽  
Gram Negative ◽  
E Coli

Sliced beef tissue was artificially contaminated with Salmonella typhimurium, Listeria monocytogenes and Escherichia coli O157:H7. The contaminated tissue was immersed in 8, 10 and 12% solutions of trisodium phosphate at 25, 40 and 55°C with contact times of up to 3 min. The concentration of the trisodium phosphate solution was not a significant factor in reducing the populations of the bacteria on either lean or adipose tissue. Reductions in bacterial populations of 1 to 1.5 log10 cycles were obtained on lean tissue contaminated with the gram-negative pathogens, although less reduction in population was seen with L. monocytogenes. Greater reductions in bacterial populations were observed on adipose tissue, with maximum reductions of 2 to 2.5 log10 cycles and 1 to 1.5 log10 cycles for the gram-negative and the gram-positive pathogens, respectively. Typically greater reductions in bacterial populations were seen as the temperature of the trisodium phosphate solution increased. Surface beef carcass tissue was inoculated with E. coli ATCC 25922 and sanitized with 8% trisodium phosphate using a model carcass washing system. Population reductions with the carcass washer and lean tissue were comparable to those observed in the laboratory with E. coli O157:H7. However, greater reductions were observed on adipose tissue from the model system, suggesting that the physical washing procedure may have contributed to the reduction in the bacterial population.

Microbiological Characterization of Human Milk1

1977 ◽  
Vol 40 (9) ◽  
pp. 614-616 ◽  
Author(s):  
A. GAVIN ◽  
K. OSTOVAR
Keyword(s):  
Staphylococcus Aureus ◽  
Breast Feeding ◽  
Staphylococcus Epidermidis ◽  
Lactobacillus Acidophilus ◽  
Bacterial Population ◽  
Streptococcus Salivarius ◽  
Streptococcus Mitis ◽  
Bacterial Populations ◽  
Milk Samples

Milk samples of five breast-feeding mothers were studied for bacterial population, flora, and source. In most instances, samples taken at postfeeding contained higher bacterial populations than prefeeding samples. Staphylococcus epidermidis was the predominant organism isolated from 100% of the samples. Increases were noticed in the appearance of Streptococcus mitis, Gaffkya tetragena, Streptococcus salivarius, Staphylococcus aureus, as well as Lactobacillus acidophilus, in the postfeeding samples. Main sources of bacteria were found to be the infant's mouth and maternal skin.

scholarly journals Crl Binds to Domain 2 of σS and Confers a Competitive Advantage on a Natural rpoS Mutant of Salmonella enterica Serovar Typhi

2010 ◽  
Vol 192 (24) ◽  
pp. 6401-6410 ◽  
Author(s):  
Véronique Monteil ◽  
Annie Kolb ◽  
Claudine Mayer ◽  
Sylviane Hoos ◽  
Patrick England ◽  
...  
Keyword(s):  
Competitive Advantage ◽  
Salmonella Enterica ◽  
Bacterial Population ◽  
Wild Type ◽  
Bacterial Populations ◽  
Salmonella Enterica Serovar Typhi ◽  
Bacterial Response ◽  
Modeled Structure ◽  
Rpos Mutant ◽  
Two Hybrid

ABSTRACTThe RpoS sigma factor (σS) is the master regulator of the bacterial response to a variety of stresses. Mutants inrpoSarise in bacterial populations in the absence of stress, probably as a consequence of a subtle balance between self-preservation and nutritional competence. We characterized here one naturalrpoSmutant ofSalmonella entericaserovar Typhi (Ty19). We show that therpoSallele of Ty19 (rpoSTy19) led to the synthesis of a σSTy19protein carrying a single glycine-to-valine substitution at position 282 in σSdomain 4, which was much more dependent than the wild-type σSprotein on activation by Crl, a chaperone-like protein that increases the affinity of σSfor the RNA polymerase core enzyme (E). We used the bacterial adenylate cyclase two-hybrid system to demonstrate that Crl bound to residues 72 to 167 of σSdomain 2 and that G282V substitution did not directly affect Crl binding. However, this substitution drastically reduced the ability of σSTy19to bind E in a surface plasmon resonance assay, a defect partially rescued by Crl. The modeled structure of the EσSholoenzyme suggested that substitution G282V could directly disrupt a favorable interaction between σSand E. TherpoSTy19allele conferred a competitive fitness when the bacterial population was wild type forcrlbut was outcompeted in Δcrlpopulations. Thus, these results indicate that the competitive advantage of therpoSTy19mutant is dependent on Crl and suggest thatcrlplays a role in the appearance ofrpoSmutants in bacterial populations.

scholarly journals Holdover Inoculum of Pseudomonas syringae pv. alisalensis from Broccoli Raab Causes Disease in Subsequent Plantings

Plant Disease ◽  
2006 ◽  
Vol 90 (8) ◽  
pp. 1077-1084 ◽  
Author(s):  
N. A. Cintas ◽  
S. T. Koike ◽  
R. A. Bunch ◽  
C. T. Bull
Keyword(s):  
Pseudomonas Syringae ◽  
Brassica Rapa ◽  
Bacterial Blight ◽  
Laboratory Tests ◽  
Bacterial Population ◽  
Disease Incidence ◽  
Untreated Soil ◽  
Bacterial Populations ◽  
Field Soils ◽  
Over Time

Uniform plots of broccoli raab (Brassica rapa subsp. rapa) seedlings were inoculated with a rifampicin-resistant strain of Pseudomonas syringae pv. alisalensis, the causal agent of bacterial blight on crucifers, resulting in 100% disease incidence in mature plants. Diseased plants were incorporated into the soil at maturity and smaller replicated plots were replanted at various times after incorporation. Rifampicin-resistant fluorescent pseudomonads with rep-PCR profiles identical to P. syringae pv. alisalensis were isolated from lesions on plants grown in soil into which the first diseased crop was incorporated. Disease incidence declined in mature plants as the length of time between incorporation of the first planting and seeding of the replanted plots increased. Bacterial population levels in soil decreased over time and bacteria were no longer detectable 3 weeks after incorporation of the diseased crop. In laboratory tests, population levels of P. syringae pv. alisalensis decreased in untreated soil but not in autoclaved soil. Greenhouse studies demonstrated a direct correlation between population levels of P. syringae pv. alisalensis applied to soil and disease incidence in seedlings. However, the decline in bacterial populations in field soils did not wholly account for the decline in disease incidence with subsequent plantings.

scholarly journals Detection of Viable Bacteria during Sludge Ozonation by the Combination of ATP Assay with PMA-Miseq Sequencing

Water ◽  
2017 ◽  
Vol 9 (3) ◽  
pp. 166 ◽  
Author(s):  
Shaonan Tian ◽  
Zhe Tian ◽  
Hong Yang ◽  
Min Yang ◽  
Yu Zhang
Keyword(s):  
Bacterial Population ◽  
Sewage Treatment ◽  
Reduction Rate ◽  
Municipal Sewage ◽  
Miseq Sequencing ◽  
Bacterial Populations ◽  
Atp Assay ◽  
Viable Bacteria ◽  
Viable Biomass ◽  
Polymerase Chain

Using sludge obtained from municipal sewage treatment plants, the response of viable bacterial populations during the sludge ozonation process was investigated by a combination of adenosine triphosphate (ATP) assay and propidium monoazide (PMA)-Miseq sequencing. The ATP assay was first optimized for application on sludge samples by adjusting the sludge solid contents and reaction time. PMA-modified polymerase chain reaction (PCR) was also optimized by choosing the suitable final PMA concentration. The quantity and composition of viable bacterial populations during sludge ozonation were further elucidated using the optimized ATP and PMA-modified PCR methods. The results indicated that after the sludge was exposed to ozone (O3) at 135 mg·O3/g total suspended solids (TSS), the viable biomass displayed a substantial decrease, with a reduction rate reaching 70.89%. The composition of viable bacterial communities showed a faster succession, showing that an ozone dosage of 114 mg·O3/g TSS is enough to significantly change the viable bacterial population structure. Floc-forming genera, such as Zoogloea, Ferruginibacter, Thauera and Turneriella, are sensitive to ozonation, while the relative abundances of some functional bacterial genera, including SM1A02, Nitrospira and Candidatus Accumulibacter, remained constant or increased in the viable bacterial population during sludge ozonation, indicating that they are more resistant to ozonation.

ENDOPHYTIC BACTERIAL FLORA IN SOLANUM TUBEROSUM AND ITS SIGNIFICANCE IN BACTERIAL RING ROT DIAGNOSIS

1974 ◽  
Vol 54 (1) ◽  
pp. 115-122 ◽  
Author(s):  
S. H. DE BOER ◽  
R. J. COPEMAN
Keyword(s):  
Solanum Tuberosum ◽  
Bacterial Population ◽  
Bacterial Flora ◽  
Stem Tissue ◽  
Bacterial Ring Rot ◽  
Bacterial Populations ◽  
Corynebacterium Sepedonicum ◽  
Potato Plants ◽  
Ring Rot ◽  
Significant Difference

The aerobic endophytic bacterial population in "healthy" potato plants was found to vary from fewer than 1 × 103 to 4.2 × 107 cells/cm3 of stem tissue and from 0 to 1.6 × 104 cells/cm3 in tubers. No significant correlation was found between the bacterial population in stems and tubers of the same plant, nor was there a significant difference in the bacterial populations of virus-free plants when compared with PVX-infected plants. Strains of Micrococcus, Pseudomonas, Bacillus, Flavobacterium, Xanthomonas, Agrobacterium, and coryneforms were isolated in addition to several isolates that could not be identified. All isolates were nonpathogenic, including the coryneforms, some of which were morphologically indistinguishable from Corynebacterium sepedonicum but which were biochemically different.

The community structure of Lake Kinneret (Israel) microorganism populations: size distribution and succession

2000 ◽  
Vol 42 (1-2) ◽  
pp. 49-54 ◽  
Author(s):  
T. Bergstein Ben-Dan ◽  
D. Wynne ◽  
B. Shteinman ◽  
Z. Hu ◽  
Y. Kamenir
Keyword(s):  
Size Distribution ◽  
Bacterial Population ◽  
Vertical Plane ◽  
Term Effect ◽  
Lake Kinneret ◽  
Bacterial Populations ◽  
Long Term Effect ◽  
Bacterial Succession ◽  
Total P

The abundance and succession of bacterial populations, and their biovolume has been studied in the deepest station of Lake Kinneret, Israel during spring–summer. These parameters were then related to the chemical, biological and physical/hydromechanical conditions in the lake. Medium sized cells (2–3 μm) dominated the bacterial population in the spring, then in mid-summer the smaller cell fraction (1 μm) took over. Relatively low numbers of large cells (10 μm) were counted, but the biovolume of this fraction was significant, especially in mid-summer. Both the abundance and biovolume of medium sized cells were positively correlated with NH4+ and O2 concentrations, but not with NO3–, inorganic orthophosphate (Pi) and Total-P. At water temperatures above 28°C, the biovolume of medium sized cells decreased, probably due to faster grazing of zooplankton. When water circulation in the vertical plane was dominant, large cells disappeared from the water column, due to sinking to the bottom. We conclude that chemical parameters, such as NH4+ and O2 concentrations, had a long-term effect on bacterial succession and size distribution, whereas hydromechanical mechanisms, such as turbulent mixing in the horizontal or vertical planes, had a short-term effect.

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