scholarly journals Mathematical Analysis of Growth and Interaction Dynamics of Streptomycetes and a Bacteriophage in Soil

2000 ◽  
Vol 66 (9) ◽  
pp. 3868-3877 ◽  
Author(s):  
N. J. Burroughs ◽  
P. Marsh ◽  
E. M. H. Wellington
Keyword(s):  
Liquid Culture ◽  
Burst Size ◽  
Agar Plate ◽  
Quantitative Agreement ◽  
Host Population ◽  
Soil Environment ◽  
Host Interaction ◽  
Primary Determinant ◽  
Host Life ◽  
Underlying Mechanisms

ABSTRACT We observed the infection cycle of the temperate actinophage KC301 in relation to the growth of its host Streptomyces lividansTK24 in sterile soil microcosms. Despite a large increase in phage population following germination of host spores, there was no observable impact on host population numbers as measured by direct plate counts. The only change in the host population following infection was the establishment of a small subpopulation of KC301 lysogens. The interaction of S. lividans and KC301 in soil was analyzed with a population-dynamic mathematical model to determine the underlying mechanisms of this low susceptibility to phage attack relative to aquatic environments. This analysis suggests that the soil environment is a highly significant component of the phage-host interaction, an idea consistent with earlier observations on the importance of the environment in determining host growth and phage-host dynamics. Our results demonstrate that the accepted phage-host interaction and host life cycle, as determined from agar plate studies and liquid culture, is sufficient for quantitative agreement with observations in soil, using soil-determined rates. There are four significant effects of the soil environment: (i) newly germinated spores are more susceptible to phage lysis than are hyphae of developed mycelia, (ii) substrate mycelia in mature colonies adsorb about 98% of the total phage protecting susceptible young hyphae from infection, (iii) the burst size of KC301 is large in soil (>150, 90% confidence) relative to that observed in liquid culture (120, standard error of the mean [SEM], 6), and (iv) there is no measurable impact on the host in terms of reduced growth by the phage. We hypothesize that spatial heterogeneity is the principal cause of these effects and is the primary determinant in bacterial escape of phage lysis in soil.

scholarly journals Intimate relationships among soil bacteria: actinomycetes and mycolic acid-containing bacteria

2021 ◽  
Author(s):  
Manami Kato ◽  
Shumpei Asamizu ◽  
Hiroyasu Onaka
Keyword(s):  
Intimate Relationships ◽  
Soil Bacteria ◽  
Liquid Culture ◽  
Mycolic Acid ◽  
Metabolic Changes ◽  
Natural Soil ◽  
Selective Screening ◽  
Soil Environment ◽  
Aggregate Form ◽  
Single Strain

Abstract Co-culture is an efficient strategy for natural product discovery. We have used mycolic acid-containing bacteria (MACB) Tsukamurella pumonis TP-B0596 to induce secondary metabolism by actinomycetes and have found several natural products. We also observed that MACB attached to the mycelium of Streptomyces lividans forming coaggregates during combined-culture. This stimulated interest in the interactions among actinomycetes and MACB, and we found that soil isolated cultures contained a mixture of actinomycetes and MACB. Our previously observed interactions were the result of selective screening and combination of bacteria in the lab, which warranted investigation of the existence of these interactions in the natural soil environment. Therefore, in this paper, we report the interaction between a co-isolated natural pair of actinomycetes and MACB in terms of morphology and metabolic changes. A natural pair of actinomycetes and MACB co-aggregated in liquid culture and showed metabolic changes. Interestingly, co-aggregated actinomycetes and MACB were re-isolated from soil with no obvious morphological colony differences from the colony of a single strain. The results demonstrate that there is a stochastic chance of picking colonies containing co-aggregated actinomycetes and MACB, which suggests that the pair can exist in co-aggregate form in the soil environment and interact with each other.

scholarly journals Morphological, biological, and genomic characterization of a newly isolated lytic phage Sfk20 infecting Shigella flexneri, Shigella sonnei, and Shigella dysenteriae1

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bani Mallick ◽  
Payel Mondal ◽  
Moumita Dutta
Keyword(s):  
Burst Size ◽  
Shigella Flexneri ◽  
Alternative Therapy ◽  
Genomic Analysis ◽  
Multidrug Resistant ◽  
Lytic Activity ◽  
Lytic Phage ◽  
Tem Analysis ◽  
Host Interaction ◽  
Outbreak Area

AbstractShigellosis, caused by Shigella bacterial spp., is one of the leading causes of diarrheal morbidity and mortality. An increasing prevalence of multidrug-resistant Shigella species has revived the importance of bacteriophages as an alternative therapy to antibiotics. In this study, a novel bacteriophage, Sfk20, has been isolated from water bodies of a diarrheal outbreak area in Kolkata (India) with lytic activity against many Shigella spp. Phage Sfk20 showed a latent period of 20 min and a large burst size of 123 pfu per infected cell in a one-step growth analysis. Phage-host interaction and lytic activity confirmed by phage attachment, intracellular phage development, and bacterial cell burst using ultrathin sectioning and TEM analysis. The genomic analysis revealed that the double-stranded DNA genome of Sfk20 contains 164,878 bp with 35.62% G + C content and 241 ORFs. Results suggested phage Sfk20 to include as a member of the T4 myoviridae bacteriophage group. Phage Sfk20 has shown anti-biofilm potential against Shigella species. The results of this study imply that Sfk20 has good possibilities to be used as a biocontrol agent.

scholarly journals Last-come, best served? Mosquito biting order and Plasmodium transmission

2020 ◽  
Vol 287 (1939) ◽  
pp. 20202615
Author(s):  
J. Isaïa ◽  
A. Rivero ◽  
O. Glaizot ◽  
P. Christe ◽  
R. Pigeault
Keyword(s):  
Host Population ◽  
Environmental Stochasticity ◽  
Parasite Transmission ◽  
Temporal Heterogeneity ◽  
Mosquito Vectors ◽  
Plastic Response ◽  
Multiple Factors ◽  
Parasite Infections ◽  
Underlying Mechanisms ◽  
Plasmodium Transmission

A pervasive characteristic of parasite infections is their tendency to be overdispersed. Understanding the mechanisms underlying this overdispersed distribution is of key importance as it may impact the transmission dynamics of the pathogen. Although multiple factors ranging from environmental stochasticity to inter-individual heterogeneity may explain parasite overdispersion, parasite infection is also overdispersed in an inbred host population maintained under laboratory conditions, suggesting that other mechanisms are at play. Here, we show that the aggregated distribution of malaria parasites within mosquito vectors is partially explained by a temporal heterogeneity in parasite infectivity triggered by the bites of mosquitoes. Parasite transmission tripled between the mosquito's first and last blood feed in a period of only 3 h. Surprisingly, the increase in transmission is not associated with an increase in parasite investment in production of the transmissible stage. Overall, we highlight that Plasmodium is capable of responding to the bites of mosquitoes to increase its own transmission at a much faster pace than initially thought and that this is partly responsible for overdispersed distribution of infection. We discuss the underlying mechanisms as well as the broader implications of this plastic response for the epidemiology of malaria.

Sexual pheromone accumulation and response in agar plate and liquid cultures of Dictyostelium discoideum

1982 ◽  
Vol 28 (11) ◽  
pp. 1273-1276 ◽  
Author(s):  
Paul S. Morris ◽  
Keith E. Lewis ◽  
Danton H. O'Day
Keyword(s):  
Dictyostelium Discoideum ◽  
Liquid Culture ◽  
Agar Plate ◽  
Maximal Activity ◽  
Sexual Pheromone ◽  
Isolation And Characterization ◽  
Sexual Pheromones ◽  
Slime Moulds ◽  
Cellular Slime ◽  
Pheromonal Activity

Sexual development in the mated cultures of Dictyostelium discoideum is initiated by one or more pheromones. In agar plate cultures of NC4, the presence of the pheromone becomes detectable by 22 h and reaches its maximal activity by 24 h. Cells of V12 from plate cultures also reach their maximal responsiveness at 24 h. In liquid culture, the NC4 pheromonal activity is detectable by 10 h and increases to a maximum at 15 h before declining so that by 30 h no activity is detectable. The V12 cells develop the competence to respond to the pheromone by 10 h and increase to a peak responsiveness by 15 h after which they lose the ability to respond. These data support earlier experiments demonstrating that sexual pheromones exist in the cellular slime moulds. The results of the liquid culture experiments in which the pheromonal induction of macrocyst formation reaches levels equivalent to 30% of mated cultures (NC4 × V12) also suggest that this pheromone bioassay system is sensitive enough to permit the isolation and characterization of the sexual pheromones of D. discoideum.

scholarly journals Dynamic modelling of viral impact on cyanobacterial populations in shallow lakes: implications of burst size

2006 ◽  
Vol 86 (3) ◽  
pp. 537-542 ◽  
Author(s):  
Herman J. Gons ◽  
Hans L. Hoogveld ◽  
Stefan G.H. Simis ◽  
Marjolijn Tijdens
Keyword(s):  
Burst Size ◽  
Dynamic Modelling ◽  
Nutrient Status ◽  
Host Cells ◽  
Ecological Implication ◽  
Eutrophic Lakes ◽  
Host Interaction ◽  
Water Columns ◽  
Single Host ◽  
Large Burst

Laboratory experiments with whole water-columns from shallow, eutrophic lakes repeatedly showed collapse of the predominant filamentous cyanobacteria. The collapse could be due to viral activity, from the evidence of electron microscopy of infected cyanobacterial cells and observed dynamics of virus-like particles. Burst-size effects on single-host single-virus dynamics was modelled for nutrient-replete growth of the cyanobacteria and fixed viral decay rate in the water column. The model combined previously published equations for nutrient-replete cyanobacterial growth and virus–host relationship. According to the model results, burst sizes greater than 200 to 400 virions per cell would result in host extinction, whereas lower numbers would allow coexistence, and even stable population densities of host and virus. High-nutrient status of the host cells might accommodate a large burst size. The ecological implication could be that burst-size increase accompanying a transition from phosphorus to light-limited cyanobacterial growth might destabilize the virus–host interaction and result in the population collapse observed in the experiments.

scholarly journals Long COVID a New Derivative in the Chaos of SARS-CoV-2 Infection: The Emergent Pandemic?

2021 ◽  
Vol 10 (24) ◽  
pp. 5799
Author(s):  
Diego Fernández-Lázaro ◽  
Nerea Sánchez-Serrano ◽  
Juan Mielgo-Ayuso ◽  
Juan Luis García-Hernández ◽  
Jerónimo J. González-Bernal ◽  
...  
Keyword(s):  
Pediatric Patients ◽  
Current Knowledge ◽  
Specific Treatment ◽  
Organ Damage ◽  
Pharmacological Treatments ◽  
Gut Flora ◽  
Host Interaction ◽  
Symptom Complex ◽  
Underlying Mechanisms ◽  
Immunological Alterations

Coronavirus disease 2019 (COVID-19) is a multisystem illness caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which can manifest with a multitude of symptoms in the setting of end-organ damage, though it is predominantly respiratory. However, various symptoms may remain after acute SARS-CoV-2 infection, and this condition is referred to as “Long COVID” (LC). Patients with LC may develop multi-organ symptom complex that remains 4–12 weeks after the acute phase of illness, with symptoms intermittently persisting over time. The main symptoms are fatigue, post-exertional malaise, cognitive dysfunction, and limitation of functional capacity. Pediatric patients developed the main symptoms of LC like those described in adults, although there may be variable presentations of LC in children. The underlying mechanisms of LC are not clearly known, although they may involve pathophysiological changes generated by virus persistence, immunological alterations secondary to virus–host interaction, tissue damage of inflammatory origin and hyperactivation of coagulation. Risk factors for developing LC would be female sex, more than five early symptoms, early dyspnea, previous psychiatric disorders, and alterations in immunological, inflammatory and coagulation parameters. There is currently no specific treatment for LC, but it could include pharmacological treatments to treat symptoms, supplements to restore nutritional, metabolic, and gut flora balance, and functional treatments for the most disabling symptoms. In summary, this study aims to show the scientific community the current knowledge of LC.

Infestation intensity and prevalence of an ectosymbiotic midge under variable environmental and host conditions

2002 ◽  
Vol 80 (12) ◽  
pp. 2061-2071 ◽  
Author(s):  
C M Pennuto ◽  
C L Wooster-Brown ◽  
C A Belisle
Keyword(s):  
Population Dynamics ◽  
Attachment Site ◽  
Host Density ◽  
Host Population ◽  
Intraspecific Interactions ◽  
Abiotic Conditions ◽  
Host Interaction ◽  
Infestation Intensity ◽  
Obligate Symbiont ◽  
General Expectation

Host–symbiont theory suggests that the abundance of an obligate symbiont will correlate positively with the density and size of its host. We examined these expectations using an obligate chironomid ectosymbiont – host fishfly (Nanocladius (Plecopteracoluthus) sp. No. 5 – Nigronia serricornis) system in 13 streams of southern Maine over 2 years (1996–1998). In addition, we investigated field conditions and macroinvertebrate-community composition, to search for correlates with symbiont prevalence and mean infestation intensity. Prevalence and infestation intensity were high in both years of the study, but neither infestation intensity nor prevalence was correlated with host population density across sites. Within sites, prevalence increased significantly when host density declined, contrary to our expectation. Symbiont-infestation intensity was not related to host size. No symbiont-population attributes correlated with physicochemical conditions in either sample year but prevalence was positively correlated with infestation intensity. Ectosymbiotic midges exhibited a significant host and attachment-site bias. Collectively, these data suggest that this symbiont–host interaction is obligate and stable, but the dynamics in our streams do not support the general expectation of increasing symbiont-population size with either increasing host-population or body size. Intraspecific interactions between symbionts are thought to have a stronger influence on population dynamics than do host populations or abiotic conditions for this ectosymbiotic midge.

Numerical Study of the Unsteady Blade Row Interaction in a Three-Stage Low Pressure Turbine

2003 ◽  
Author(s):  
Christian Nayeri ◽  
Wolfgang Ho¨hn
Keyword(s):  
Numerical Study ◽  
Time Integration ◽  
Quantitative Agreement ◽  
Navier Stokes ◽  
Implicit Time ◽  
Surface Pressure Distribution ◽  
Computational Mesh ◽  
Transition Models ◽  
Underlying Mechanisms ◽  
Turbulence Parameters

The focus of this paper is on the one hand the quantitative optimization of the unsteady numerical simulations compared to experiments, and on the other hand to gain a better insight into the underlying mechanisms when an upstream wake of a stator interacts with the flow-field of the next stator. This was achieved by optimizing the numerical turbulence parameters used in the turbulence and transition models. Using steady calculations an optimal initial solution for the unsteady calculation was found. Also, the computational mesh was refined. For the numerical computations a time accurate Reynolds averaged Navier-Stokes solver is applied. Turbulence is modeled using the Spalart-Allmaras one equation turbulence model. The integration of the governing equations in time is performed by an implicit time integration for the steady calculations, and by an implicit dual time stepping scheme for the unsteady calculations. At the inlet and outlet reflecting or non-reflecting boundary conditions are used. The quasi 3D calculations are conducted on a stream surface around midspan allowing a varying stream tube thickness. The results show that by adjusting the turbulence parameters in the turbulence and transition models, a better qualitative and quantitative agreement between experiments and numerical results can be achieved. Steady and unsteady quantities are shown, e.g. the surface pressure distribution and the wall shear stress. The unsteady simulations of two different azimuthal positions of the first and third stator reveal different evolutions of the boundary layers of the second and third stators due to the influence of the wake of the upstream stators. These differences are better captured through the above mentioned improvements, i.e. reduction of sheared cells in the computational mesh and optimization of turbulence and transition parameters in the allowable range of the models.

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