scholarly journals Relative Contributions ofHalobacteriovoraxand Bacteriophage to Bacterial Cell Death under Various Environmental Conditions

mBio ◽  
2018 ◽  
Vol 9 (4) ◽  
Author(s):  
Huan Chen ◽  
Edward A. Laws ◽  
Julio L. Martin ◽  
Timkhite-Kulu Berhane ◽  
Paul A. Gulig ◽  
...  
Keyword(s):  
Food Web ◽  
Environmental Conditions ◽  
Vibrio Vulnificus ◽  
Microbial Food Web ◽  
Nutrient Media ◽  
Bacterial Mortality ◽  
Content Type ◽  
Practical Applications ◽  
Cycling Of Nutrients

ABSTRACTThe role of protists and bacteriophages in bacterial predation in the microbial food web has been well studied. There is mounting evidence thatBdellovibrioand like organisms (BALOs) also contribute to bacterial mortality and, in some cases, more so than bacteriophages. A full understanding of the ecologic function of the microbial food web requires recognition of all major predators and the magnitude of each predator’s contribution. Here we investigated the contribution ofHalobacteriovorax, one of the BALOs, and bacteriophages when incubated with their common prey,Vibrio vulnificus, in a seawater microcosm. We observed thatHalobacteriovoraxwas the greatest responder to the prey, increasing 18-fold with a simultaneous 4.4-log-unit reduction ofV. vulnificusat 40 h, whereas the bacteriophage population showed no significant increase. In subsequent experiments to formulate a medium that would support the predatory activities and replication of both predators, low-nutrient media favored the predation and replication of theHalobacteriovorax, whereas higher-nutrient media enhanced phage growth. The greatest prey reduction and replication of bothHalobacteriovoraxand phage were observed in media with moderate nutrient levels. Additional experiments show that the predatory activities of both predators were influenced by environmental conditions, specifically, temperature and salinity. The two predators combined exerted greater control onV. vulnificus, a synergism that may be exploited for practical applications to reduce bacterial populations. These findings suggest that along with bacteriophage and protists,Halobacteriovoraxhas the potential to have a prominent role in bacterial mortality and cycling of nutrients, two vital ecologic functions.IMPORTANCEAlthough much has been reported about the marine microbial food web and the role of micropredators, specifically viruses and protists, the contribution ofBdellovibrio-like predators has largely been ignored, posing a major gap in understanding food web processes. A complete scenario of the microbial food web cannot be developed until the roles of all major micropredators and the magnitude of their contributions to bacterial mortality, structuring of microbial communities, and cycling of nutrients are assessed. Here we show compelling evidence thatHalobacteriovorax, a predatory bacterium, is a significant contributor to bacterial death and, in some cases, may rival viruses as agents of bacterial mortality. These results advance current understanding of the microbial loop and top-down control on the bacterial community.

scholarly journals The concept and application of ḍamān al-milkiyyah (ownership risk)

2017 ◽  
Vol 9 (2) ◽  
pp. 148-163 ◽  
Author(s):  
Lutfi Abdul Razak ◽  
Muhammad Nabil Saupi
Keyword(s):  
Design Methodology ◽  
Islamic Law ◽  
Content Type ◽  
Practical Applications ◽  
For Profit ◽  
Descriptive Research ◽  
Financial Products ◽  
Financial Transactions ◽  
Practical Implications

Purpose The purpose of this paper is to elucidate the concept of ḍamān al-milkiyyah (ownership risk) and to assess its application in contemporary Islamic financial products and services. Design/methodology/approach The methodology adopted is that of descriptive research. Findings From an Islamic law of contract perspective, the concept of ḍamān al-milkiyyah is central to legitimate profit-making transactions and hence must be adhered to in practical applications of Islamic finance. Research limitations/implications This study should help motivate further investigation into the position of ḍamān al-milkiyyah among different parties in existing Islamic financial products and services. Practical implications Policymakers and regulators should ensure that Islamic financial products and services are structured in a way that does not allow parties to profit without adequately bearing the liability for potential loss. Social implications The condition of ḍamān al-milkiyyah as a source of legitimate profit reflects the idea that the role of finance in Islam is to promote and ensure social benefits. Originality/value This paper emphasizes the importance of ḍamān al-milkiyyah as a fundamental condition for profit in Islamic financial transactions.

scholarly journals Adaptations of the Secretome of Candida albicans in Response to Host-Related Environmental Conditions

2015 ◽  
Vol 14 (12) ◽  
pp. 1165-1172 ◽  
Author(s):  
Frans M. Klis ◽  
Stanley Brul
Keyword(s):  
Candida Albicans ◽  
Cell Surface ◽  
Human Body ◽  
Environmental Conditions ◽  
Surface Stress ◽  
Hyphal Growth ◽  
Content Type ◽  
General Response ◽  
Culture Supernatants

ABSTRACTThe wall proteome and the secretome of the fungal pathogenCandida albicanshelp it to thrive in multiple niches of the human body. Mass spectrometry has allowed researchers to study the dynamics of both subproteomes. Here, we discuss some major responses of the secretome to host-related environmental conditions. Three β-1,3-glucan-modifying enzymes, Mp65, Sun41, and Tos1, are consistently found in large amounts in culture supernatants, suggesting that they are needed for construction and expansion of the cell wall β-1,3-glucan layer and thus correlate with growth and might serve as diagnostic biomarkers. The genesENG1,CHT3, andSCW11, which encode an endoglucanase, the major chitinase, and a β-1,3-glucan-modifying enzyme, respectively, are periodically expressed and peak in M/G1. The corresponding protein abundances in the medium correlate with the degree of cell separation during single-yeast-cell, pseudohyphal, and hyphal growth. We also discuss the observation that cells treated with fluconazole, or other agents causing cell surface stress, form pseudohyphal aggregates. Fluconazole-treated cells secrete abundant amounts of the transglucosylase Phr1, which is involved in the accumulation of β-1,3-glucan in biofilms, raising the question whether this is a general response to cell surface stress. Other abundant secretome proteins also contribute to biofilm formation, emphasizing the important role of secretome proteins in this mode of growth. Finally, we discuss the relevance of these observations to therapeutic intervention. Together, these data illustrate thatC. albicansactively adapts its secretome to environmental conditions, thus promoting its survival in widely divergent niches of the human body.

scholarly journals The role of ciliates within the microbial food web in the eutrophicated part of Kaštela Bay (Middle Adriatic Sea)

2006 ◽  
Vol 70 (3) ◽  
pp. 431-442 ◽  
Author(s):  
Natalia Bojanic ◽  
Mladen Šolic ◽  
Nada Krstulovic ◽  
Stefanija Šestanovic ◽  
Živana Nincevic Gladan ◽  
...  
Keyword(s):  
Food Web ◽  
Adriatic Sea ◽  
Microbial Food Web

scholarly journals Eco-Biology of Photosynthetic Picoeukaryotes in a Monsoon Influenced Tropical Bay: A Flow Cytometric and Chemotaxonomic Approach

2021 ◽  
Author(s):  
Smita Mitbavkar ◽  
Samantha D'souza
Keyword(s):  
Food Web ◽  
Environmental Conditions ◽  
High Performance ◽  
Microbial Food Web ◽  
Nutrient Concentrations ◽  
Flow Cytometric ◽  
South West Monsoon ◽  
Total Phytoplankton ◽  
West Monsoon ◽  
Tropical Bay

Abstract The composition and ecology of photosynthetic picoeukaryotes (PPEUK) are essential for microbial food web functioning. We hypothesize that the simultaneous use of flow cytometry (FCM) and High-Performance-Liquid-Chromatography (HPLC) tools will aid in discerning the dominant PPEUK groups contributing to abundance and biomass under prevailing environmental conditions. The PPEUK seasonal community abundance and pigment biomass were investigated from a south-west monsoon influenced tropical bay from June 2015-May 2016. A size-fractionated (< 3 µm) approach using FCM and HPLC revealed five and six PPEUK groups, respectively. Picocryptophytes dominated the PPEUK biomass under varied environmental conditions, whereas Picodiatoms contributed substantially, being abundant under turbulent, low-temperature, nutrient (NO3−, SiO44−) enriched conditions. The Picochlorophytes dominated the community numerically. The relatively higher abundance and biomass of Picoprasinophytes and a positive correlation with NO3− and NH4+ imply proliferation under higher nutrient concentrations. The least contributors to biomass were Picodinoflagellates and Picoprymnesiophytes. The relatively larger cell size of Picocryptophytes and Picodiatoms resulted in higher cumulative biomass, signifying their role in the microbial food web. Our study proposes incorporation of additional indicator pigments in algorithms used to estimate coastal picophytoplankton contribution to total phytoplankton biomass to avoid discrepancies.

scholarly journals The Bacterial Tyrosine Kinase Activator TkmA Contributes to Biofilm Formation Largely Independently of the Cognate Kinase PtkA in Bacillus subtilis

2015 ◽  
Vol 197 (21) ◽  
pp. 3421-3432 ◽  
Author(s):  
Tantan Gao ◽  
Jennifer Greenwich ◽  
Yan Li ◽  
Qi Wang ◽  
Yunrong Chai
Keyword(s):  
Bacillus Subtilis ◽  
Tyrosine Kinase ◽  
Cross Talk ◽  
Environmental Conditions ◽  
Tyrosine Kinases ◽  
Biofilm Formation ◽  
Potassium Phosphate ◽  
Cell Physiology ◽  
Content Type

ABSTRACTInBacillus subtilis, biosynthesis of exopolysaccharide (EPS), a key biofilm matrix component, is regulated at the posttranslational level by the bacterial tyrosine kinase (BY-kinase) EpsB. EpsB, in turn, relies on the cognate kinase activator EpsA for activation. A concerted role of a second BY-kinase–kinase activator pair, PtkA and TkmA, respectively in biofilm formation was also indicated in previous studies. However, the exact functions of PtkA and TkmA in biofilm formation remain unclear. In this work, we show that the kinase activator TkmA contributes to biofilm formation largely independently of the cognate kinase, PtkA. We further show that the biofilm defect caused by a ΔtkmAmutation can be rescued by complementation byepsA, suggesting a functional overlap between TkmA and EpsA and providing a possible explanation for the role of TkmA in biofilm formation. We also show that the importance of TkmA in biofilm formation depends largely on medium conditions; the biofilm defect of ΔtkmAis very severe in the biofilm medium LBGM (lysogenic broth [LB] supplemented with 1% [vol/vol] glycerol and 100 μM MnSO4) but marginal in another commonly used biofilm medium, MSgg (5 mM potassium phosphate [pH 7.0], MOPS [100 mM morpholinepropanesulfonic acid] [pH 7.0], 2 mM MgCl2, 700 μM CaCl2, 50 μM MnCl2, 50 μM FeCl3, 1 μM ZnCl2, 2 μM thiamine, 0.5% glycerol, 0.5% glutamic acid, 50 μg/ml tryptophan, 50 μg/ml threonine, and 50 μg/ml phenylalanine). The molecular basis for the medium dependence is likely due to differential expression oftkmAandepsAin the two different media and complex regulation of these genes by both Spo0A and DegU. Our studies provide genetic evidence for possible cross talk between a BY-kinase activator (TkmA) and a noncognate kinase (EpsB) and an example of how environmental conditions may influence such cross talk in regulating biofilm formation inB. subtilis.IMPORTANCEIn bacteria, biosynthesis of secreted polysaccharides is often regulated by bacterial tyrosine kinases (BY-kinases). BY-kinases, in turn, rely on cognate kinase activators for activation. In this study, we investigated the role of a BY-kinase activator in biofilm formation inBacillus subtilis. We present evidence that different BY-kinase activators may functionally overlap each other, as well as an example of how activities of the BY-kinase activators may be highly dependent on environmental conditions. Our study broadens the understanding of the complexity of regulation of the BY-kinases/kinase activators and the influence on bacterial cell physiology.

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