Aquatic Reservoirs Research Articles

In silico method for predicting infectious strains of influenza A virus from its genome and protein sequences.

Influenza A is a contagious viral disease responsible for four pandemics in the past and a major public health concern. Being zoonotic in nature, the virus can cross the species barrier and transmit from wild aquatic bird reservoirs to humans via intermediate hosts. In this study, we have developed a computational method for the prediction of human-associated and non-human-associated influenza A virus sequences. The models were trained and validated on proteins and genome sequences of influenza A virus. Firstly, we have developed prediction models for 15 types of influenza A proteins using composition-based and one-hot-encoding features. We have achieved a highest AUC of 0.98 for HA protein on a validation dataset using dipeptide composition-based features. Of note, we obtained a maximum AUC of 0.99 using one-hot-encoding features for protein-based models on a validation dataset. Secondly, we built models using whole genome sequences which achieved an AUC of 0.98 on a validation dataset. In addition, we showed that our method outperforms a similarity-based approach (i.e., blast) on the same validation dataset. Finally, we integrated our best models into a user-friendly web server 'FluSPred' (https://webs.iiitd.edu.in/raghava/fluspred/index.html) and a standalone version (https://github.com/raghavagps/FluSPred) for the prediction of human-associated/non-human-associated influenza A virus strains.

Computer Vision Based Deep Learning Approach for the Detection and Classification of Algae Species Using Microscopic Images

The natural phenomenon of harmful algae bloom (HAB) has a bad impact on the quality of pure and freshwater. It increases the risk to human health, water bodies and overall aquatic ecosystem. It is necessary to continuously monitor and perform proper action against HAB. The inspection of algae blooms by using conventional methods, like algae detection under microscopes, is a difficult, expensive, and time-consuming task, however, computer vision-based deep learning models play a vital role in identifying and detecting harmful algae growth in aquatic ecosystems and water reservoirs. Many studies have been conducted to address harmful algae growth by using a CNN based model, however, the YOLO model is considered more accurate in identifying the algae. This advanced deep learning method is extensively used to detect algae and classify them according to their corresponding category. In this study, we used various versions of the convolution neural network (CNN) based on the You Only Look Once (YOLO) model. Recently YOLOv5 has been getting more attention due to its performance in real-time object detection. We performed a series of experiments on our custom microscopic images dataset by using YOLOv3, YOLOv4, and YOLOv5 to detect and classify the harmful algae bloom (HAB) of four classes. We used pre-processing techniques to enhance the quantity of data. The mean average precision (mAP) of YOLOv3, YOLOv4, and YOLO v5 is 75.3%, 83.0%, and 91.0% respectively. For the monitoring of algae bloom in freshwater, computer-aided based systems are very helpful and effective. To the best of our knowledge, this work is pioneering in the AI community for applying the YOLO models to detect algae and classify from microscopic images.

Possible Acquisition of ESBL-mediated Antimicrobial Resistance by Farmers from Aquatic Reservoir used for Bathing and Cleaning of Water Buffalos (Bubalus bubalis) with Intestinal Carriage of ESBL Producing Escherichia coli

Little information is available on the risk of human subjects for acquisition of antimicrobial resistance (AMR) from aquatic environment other than those treated with antimicrobials for aquaculture. Carriage of extended-spectrum beta-lactamase (ESBL) and carbapenemase categories of AMR by enteric bacteria in livestock have been frequently reported. Dissemination of these categories of AMR to the environment thus poses a threat for their transmission to farmers engaged in livestock care posing a severe public health hazard. A study on the prevalence of ESBL- and carbapenemase-mediated AMR among Escherichia coli isolated from earth pond environment used for bathing and cleaning of buffalos (Bubalus bubalis) and from human subjects engaged in such activity revealed isolation rate of ESBL positivity to be higher in human subjects engaged in washing and bathing of buffalos (37.5%) compared to those without engagement in such activities (20.7%) with CTX-M type ESBL, a group of class A ESBL, as the predominant molecular type (97.4%). While no carbapenemase positivity could be detected among E. coli isolated from pond environment or buffalos, small percentage of carbapenemase could be detected among the E. coli isolated from human subjects although the risk was not higher than those not associated with bathing and cleaning of buffalos. Bathing and cleaning of buffalos could potentially facilitate transmission of ESBL resistance from livestock to human subjects in pond environment.

Genotoxicity and Trace Elements Contents Analysis in Nile Tilapia (Oreochromis niloticus) Indicated the Levels of Aquatic Contamination at Three Egyptian Areas

The toxic waste and pollutants of heavy metals continuously pollute freshwater aquatic reservoirs, which have severe implications on aquatic life and human health. The present work aims to evaluate trace elements (Zn, Mn, Cu, Cd, and Pb) along with three sites, Mariout Lake, Abbassa, and River Nile Aswan in Egypt, using Nile tilapia (Oreochromis niloticus) as bioindicator. The quality assurance, health-risk assessment, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), quantitative polymerase chain reaction (qPCR), and micronucleus test were performed to investigate the effect of different trace elements on Hsp70 gene level and micronuclei formation. We observed the highest expression of Hsp70 protein band of 70 KD and stress-responsive Hsp70 gene in the liver followed by gills of Nile tilapia caught from Mariout and Abbassa, but the lowest expression was in Nile tilapia caught from Aswan. Obvious micronuclei were observed under the microscope in erythrocytes, and their number was gradually decreased in the following manner: Mariout > Abbassa > Aswan. Noticeably, Cu, Zn, and Mn contents were low. Still, Pb and Cd contents were higher than the toxicity level recommended by the Food and Agriculture Organization (FAO), The World Health Organization (WHO), and the European Commission (EC). These results showed that Hsp70's appearance at the two levels of mRNA and protein is an effective indicator for aquatic pollution besides the aberration at the chromosome level represented in the micronucleus test. Furthermore, these results showed that Nile tilapia of the Aswan region had comparatively low trace elements contamination and were suitable for consumption.

A reaction-advection-diffusion model of cholera epidemics with seasonality and human behavior change

Cholera is a water- and food-borne infectious disease caused by V. cholerae. To investigate multiple effects of human behavior change, seasonality and spatial heterogeneity on cholera spread, we propose a reaction-advection-diffusion model that incorporates human hosts and aquatic reservoir of V. cholerae. We derive the basic reproduction number [Formula: see text] for this system and then establish a threshold type result on its global dynamics in terms of [Formula: see text]. Further, we show that the bacterial loss at the downstream end of the river due to water flux can reduce the disease risk, and describe the asymptotic behavior of [Formula: see text] for small and large diffusion in a special case (where the diffusion rates of infected human and the pathogen are constant). We also study the transmission dynamics at the early stage of cholera outbreak numerically, and find that human behavior change may lower the infection level and delay the disease peak. Moreover, the relative rate of bacterial loss, together with convection rate, plays an important role in identifying the severely infected areas. Meanwhile spatial heterogeneity may dilute or amplify cholera infection, which in turn would increase the complexity of disease spread.

The Effect of Autotrophic Cultivation of Platymonas subcordiformis in Waters from the Natural Aquatic Reservoir on Hydrogen Yield

Biological processes run by microalgae are prospective but still little known methods of hydrogen production. A prerequisite for their increased advancement is the development of economically viable and efficient technologies. The study presented in this manuscript focused on determining the efficiency of biohydrogen production by P. subcordiformis using a culture medium prepared based on natural waters. The rate of P. subcordiformis biomass growth reached 317.6 ± 42.3 mgODM/dm3·d and ensured a biomass concentration of 3493 ± 465 mgODM/dm3. The percentage concentration of hydrogen in the biogas reached 63.2 ± 1.4%, and its production rate ranged from 0.53 ± 0.05 cm3/h to 0.70 ± 0.01 cm3/h.

Improved β-galactosidase Secretion in Fresh Water Fungi through Cultural Optimization

The wide range of applications of β-galactosidase has made it a candidate enzyme of study for improved yield. Most studies focused on expressing this enzyme in expressible vector(s) while sources of this enzyme are rarely investigated. Aquatic habitats harbor arrays of microorganisms that can participate in demineralization, nutrient restoration, circulation and hence confer significant properties on the habitats and significantly influence microbial interactions and metabolism. In view of this, aquatic fungal isolates were qualitatively and quantitatively screened for intracellular and extracellular β-galactosidase production. Four fungal isolates tagged SB01 and SC02 from stream identified as Aspergillus oryzae and Aspergillus niger and SC01 and SA01 from pond identified as A. oryzae and A. niger were studied. β-galactosidase gene was successfully amplified from the four isolates and their enzyme production levels were further studied. All the isolates showed considerably higher extracellular secretion than the intracellular synthesis on glucose-based medium. The production level was probed by xylose supplementation but surprisingly, the intracellular synthesis was higher than the extracellular secretion for all the isolates. In an attempt to boost the enzyme production, temperature was varied and 25 °C showed improved β-galactosidase synthesis and secretion than the 30 °C. This study revealed these filamentous fungi as candidates for β-galactosidase production and broaden the understanding of harnessing microorganisms from an aquatic reservoir for bio-production, and more importantly, revealed the intracellular accumulation of the enzyme as a bottleneck for industrial production.
 HIGHLIGHTS
 
 The wide range of applications of β-galactosidase has made it a candidate enzyme of study for improved yield
 Most studies focused on expressing this enzyme in expressible vector(s) while sources of this enzyme are rarely investigated
 Aquatic fungal isolates were qualitatively and quantitatively screened for intracellular and extracellular β-galactosidase production
 All the isolates showed considerable higher extracellular secretion than the intracellular synthesis on glucose-based medium, and vice-versa on xylose-supplemented medium, with the highest β-galactosidase synthesis and secretion efficiency occurring at 25 °C in both instances
 This study revealed these filamentous fungi as candidates for β-galactosidase production and broaden the understanding of harnessing microorganisms from an aquatic reservoir for bio-production
 
 GRAPHICAL ABSTRACT

Conceptual Profile of Vibrio Species and the Associated Physicochemical Dynamics of Some Aquatic Reservoirs in Andoni Local Government Area of Rivers State, Nigeria

Vibrio species are autochthonous in the aquatic environment, and are among the leading causes of waterborne disease outbreaks. The ecological prevalence of Vibrio spp. is however influenced by the environmental dynamics of the reservoir system. The study was therefore aimed at assessing the physicochemical as well as seasonal factors that influence the prevalence of Vibrio spp. in some communities in Andoni Local Government Area of Rivers State. A total of 28 water samples collected in two seasons, were subjected to bacteriological and physicochemical analysis, using standard procedures. The data obtained from the study showed that the physicochemical parameters were within WHO permissible limits except for pH which had mean values within the acidic range and varied between 5.51±0.32 during the wet season, and 5.78±0.79 during the dry season. Statistical analysis of the data obtained however showed that there was a significant difference (p < 0.05) in the conductivity values with respect to location, sample type (boreholes and wells) and season, TDS, Salinity and pH were however, significantly different (p < 0.05) with respect to location only. The study on the prevalence of the Vibrio spp. in the water sources showed a prevalence rate of 29.16% in the well water samples compared to the borehole water samples with 25% mean prevalence rate. The prevalence based on location further showed that Inyorong Community had the highest prevalence rate of 50%, followed by Ngo Community with 37.5% prevalence rate, while Ukwa Community had the lowest prevalence rate of 12.5 %. Also, assessment of the seasonal prevalence of the bacteria revealed the occurrence of the isolates was 37.5% and 16.6% in the wet and dry season, respectively. The presence of Vibrio spp. in these communities in Andoni Local Government Area is of a public health concern. Regular surveillance alongside preventive measures is therefore recommended for the prevention of cholera related disease outbreaks.

Conceptual Profile of Vibrio Species and the Associated Physicochemical Dynamics of Some Aquatic Reservoirs in Andoni Local Government Area of Rivers State, Nigeria

Vibrio species are autochthonous in the aquatic environment, and are among the leading causes of waterborne disease outbreaks. The ecological prevalence of Vibrio spp. is however influenced by the environmental dynamics of the reservoir system. The study was therefore aimed at assessing the physicochemical as well as seasonal factors that influence the prevalence of Vibrio spp. in some communities in Andoni Local Government Area of Rivers State. A total of 28 water samples collected in two seasons, were subjected to bacteriological and physicochemical analysis, using standard procedures. The data obtained from the study showed that the physicochemical parameters were within WHO permissible limits except for pH which had mean values within the acidic range and varied between 5.51±0.32 during the wet season, and 5.78±0.79 during the dry season. Statistical analysis of the data obtained however showed that there was a significant difference (p < 0.05) in the conductivity values with respect to location, sample type (boreholes and wells) and season, TDS, Salinity and pH were however, significantly different (p < 0.05) with respect to location only. The study on the prevalence of the Vibrio spp. in the water sources showed a prevalence rate of 29.16% in the well water samples compared to the borehole water samples with 25% mean prevalence rate. The prevalence based on location further showed that Inyorong Community had the highest prevalence rate of 50%, followed by Ngo Community with 37.5% prevalence rate, while Ukwa Community had the lowest prevalence rate of 12.5 %. Also, assessment of the seasonal prevalence of the bacteria revealed the occurrence of the isolates was 37.5% and 16.6% in the wet and dry season, respectively. The presence of Vibrio spp. in these communities in Andoni Local Government Area is of a public health concern. Regular surveillance alongside preventive measures is therefore recommended for the prevention of cholera related disease outbreaks.

HESSEL DE VRIES: RADIOCARBON PIONEER FROM GRONINGEN

ABSTRACTHessel de Vries contributed to radiocarbon (14C) dating for only one short decade. Yet, his development of proportional CO2 counting greatly facilitated 14C measurements, improved their reproducibility, and lowered both the amount of carbon needed for a measurement and the 14C detection limit by at least a factor ten. Validating Libby’s 14C method by checking its basic assumptions with improved sensitivity, de Vries documented relatively minor violations. Natural variations in atmospheric 14C concentrations, found in tree rings, marked the start of 14C tree-ring calibration. Variable differences in 14C concentration between the atmosphere and aquatic reservoirs revealed reservoir ages, leading to further studies. De Vries applied analogue modeling to gain a better understanding of the influence of cosmogenic 14C production and the global carbon cycle, inclusive CO2 exchange across the air-water boundary, on atmospheric 14C concentrations. In close collaboration with colleagues in archaeology and geology, de Vries documented climate fluctuations and archaeological developments over the last 50,000+ years and placed them on a common 14C time scale.

Photochemical (UV–vis/H2O2) degradation of carotenoids: Kinetics and molecular end products

Constraining the formation mechanisms of organic matter that persists in aquatic reservoirs is important for determining the reactivity and fate of carbon and nutrients in these environments. Recent studies have linked dissolved organic matter (DOM) accumulating in the ocean to linear terpenoid structures, and carotenoid degradation products have been proposed as potential precursors. The prevalence of reactive oxygen species in aquatic environments and their potential to be quenched by carotenoids led us to examine radical-assisted photochemical degradation of carotenoids as a potential mechanism for DOM formation and transformation. Experiments were conducted with aggregates of β-carotene, astaxanthin, fucoxanthin and meso-zeaxanthin in THF:H2O under solar light irradiation assisted by hydrogen peroxide (UV–Vis/H2O2). Based on the fine structure of UV–Vis spectra, it was determined that β-carotene and meso-zeaxanthin formed J-type aggregates in experimental solutions, while astaxanthin and fucoxanthin formed H2-type aggregates, consistent with their structural characteristics. All carotenoids degraded under the combined influence of photolysis and OH scavenging, with fucoxanthin exhibiting the fastest degradation kinetics (kPO = 3.69 10−3 s−1) and meso-zeaxanthin the slowest (kPO = 4.37 10−4 s−1). The major degradation products detected by electrospray ionization (ESI) tandem mass spectrometry (MS/MS) were apo-aldehydes and apo-ketones, with the latter tending to accumulate, but epoxidation of the carotenoids also took place, and longer irradiation times resulted in lower molecular weight products. Reaction kinetics and accumulating carotenoid oxidation products identified in this study provide potential formation mechanisms and biomarkers for examining DOM cycling.

Environmental prevalence of toxigenic Vibrio cholerae O1 in Bangladesh coincides with V. cholerae non-O1 non-O139 genetic variants which overproduce autoinducer-2

Prevalence of toxigenic Vibrio cholerae O1 in aquatic reservoirs in Bangladesh apparently increases coinciding with the occurrence of seasonal cholera epidemics. In between epidemics, these bacteria persist in water mostly as dormant cells, known as viable but non-culturable cells (VBNC), or conditionally viable environmental cells (CVEC), that fail to grow in routine culture. CVEC resuscitate to active cells when enriched in culture medium supplemented with quorum sensing autoinducers CAI-1 or AI-2 which are signal molecules that regulate gene expression dependent on cell density. V. cholerae O1 mutant strains with inactivated cqsS gene encoding the CAI-1 receptor has been shown to overproduce AI-2 that enhance CVEC resuscitation in water samples. Since V. cholerae non-O1 non-O139 (non-cholera-vibrios) are abundant in aquatic ecosystems, we identified and characterized naturally occurring variant strains of V. cholerae non-O1 non-O139 which overproduce AI-2, and monitored their co-occurrence with V. cholerae O1 in water samples. The nucleotide sequence and predicted protein products of the cqsS gene carried by AI-2 overproducing variant strains showed divergence from that of typical V. cholerae O1 or non-O1 strains, and their culture supernatants enhanced resuscitation of CVEC in water samples. Furthermore, prevalence of V. cholerae O1 in the aquatic environment was found to coincide with an increase in AI-2 overproducing non-O1 non-O139 strains. These results suggest a possible role of non-cholera vibrios in the environmental biology of the cholera pathogen, in which non-O1 non-O139 variant strains overproducing AI-2 presumably contribute in resuscitation of the latent pathogen, leading to seasonal cholera epidemics. Importance. Toxigenic Vibrio cholerae which causes seasonal epidemics of cholera persists in aquatic reservoirs in endemic areas. The bacteria mostly exist in a dormant state during inter-epidemic periods, but periodically resuscitate to the active form. The resuscitation is enhanced by signal molecules called autoinducers (AIs). Toxigenic V. cholerae can be recovered from water samples that normally test negative for the organism in conventional culture, by supplementing the culture medium with exogenous AIs. V. cholerae belonging to the non-O1 non-O139 serogroups which do not cause cholera are also abundant in natural waters, and they are capable of producing AIs. In this study we characterized V. cholerae non-O1 non-O139 variant strains which overproduce an autoinducer called AI-2, and found that the abundance of the cholera pathogen in aquatic reservoirs correlates with an increase in the AI-2 overproducing strains. Our results suggest a probable role of these variant strains in the environmental biology and epidemiology of toxigenic V. cholerae, and may lead to novel means for surveillance, prevention and control of cholera.

Vibrio cholerae's mysterious Seventh Pandemic island (VSP-II) encodes novel Zur-regulated zinc starvation genes involved in chemotaxis and cell congregation.

Vibrio cholerae is the causative agent of cholera, a notorious diarrheal disease that is typically transmitted via contaminated drinking water. The current pandemic agent, the El Tor biotype, has undergone several genetic changes that include horizontal acquisition of two genomic islands (VSP-I and VSP-II). VSP presence strongly correlates with pandemicity; however, the contribution of these islands to V. cholerae's life cycle, particularly the 26-kb VSP-II, remains poorly understood. VSP-II-encoded genes are not expressed under standard laboratory conditions, suggesting that their induction requires an unknown signal from the host or environment. One signal that bacteria encounter under both host and environmental conditions is metal limitation. While studying V. cholerae's zinc-starvation response in vitro, we noticed that a mutant constitutively expressing zinc starvation genes (Δzur) congregates at the bottom of a culture tube when grown in a nutrient-poor medium. Using transposon mutagenesis, we found that flagellar motility, chemotaxis, and VSP-II encoded genes were required for congregation. The VSP-II genes encode an AraC-like transcriptional activator (VerA) and a methyl-accepting chemotaxis protein (AerB). Using RNA-seq and lacZ transcriptional reporters, we show that VerA is a novel Zur target and an activator of the nearby AerB chemoreceptor. AerB interfaces with the chemotaxis system to drive oxygen-dependent congregation and energy taxis. Importantly, this work suggests a functional link between VSP-II, zinc-starved environments, and energy taxis, yielding insights into the role of VSP-II in a metal-limited host or aquatic reservoir.

Natural community of macroalgae from chromium-contaminated site for effective remediation of Cr(VI)-containing leachates

The natural macroalgal community, which developed in the unique and extremely Cr(VI)-polluted aquatic reservoir situated near a historical chromium-waste landfill, was studied in order to recognize the main mechanisms of Cr(VI) detoxification by the algal species. The conducted taxonomic analysis revealed mixed composition of the filamentous forms of algae and showed that three species of Tribonema, namely T. vulgare, T. microchloron and T. viride, which have not been studied before with regard to the mechanisms of Cr(VI) removal, are likely responsible for the effective bioremediation of this highly Cr(VI)-polluted habitat. The studied algal community, with the ability to grow in extremely high concentrations of Cr(VI), i.e. up to ca. 6150 times the upper limit for surface water, exhibited hyperaccumulative properties for chromium (max 16230 mg/kg dry weight) under the given environmental conditions. We found that the main mechanism of Cr(VI) detoxification was reduction followed by Cr(III) biosorption – feasibly by ion exchange and complexation mechanisms – and that the excellent efficiency of chromium reduction under the given, unfavorable weakly alkaline conditions indicates the biological origin of this process. It was concluded that the examined reservoir inhabited by the algal community can be used, after some modifications, as a simple cost-effective “bioreactor” allowing the reduction of chromium concentration to the desired level. Moreover, the conducted studies are also essential to obtain in-depth knowledge and should also be helpful in the relevance of the community for its further application as a potential biosorbent of Cr(VI) on a global scale.

Cra and cAMP Receptor Protein Have Opposing Roles in the Regulation of fruB in Vibrio cholerae.

The Gram-negative bacterium Vibrio cholerae adapts to changes in the environment by selectively producing the necessary machinery to take up and metabolize available carbohydrates. The import of fructose by the fructose-specific phosphoenolpyruvate (PEP) phosphotransferase system (PTS) is of particular interest because of its putative connection to cholera pathogenesis and persistence. Here, we describe the expression and regulation of fruB, which encodes an EIIA-FPr fusion protein as part of the fructose-specific PTS in V. cholerae Using a series of transcriptional reporter fusions and additional biochemical and genetic assays, we identified Cra (catabolite repressor/activator) and cAMP receptor protein (CRP) as regulators of fruB expression and determined that this regulation is dependent upon the presence or absence of PTS sugars. Cra functions as a repressor, downregulating fruB expression in the absence of fructose when components of PTSFru are not needed. CRP functions as an activator of fruB expression. We also report that Cra and CRP can affect fruB expression independently; however, CRP can modulate cra expression in the presence of fructose and glucose. Evidence from this work provides the foundation for continued investigations into PTSFru and its relationship to the V. cholerae life cycle.IMPORTANCEVibrio cholerae is the causative agent of cholera disease. While current treatments of care are accessible, we still lack an understanding of the molecular mechanisms that allow V. cholerae to survive in both aquatic reservoirs and the human small intestine, where pathogenesis occurs. Central to V. cholerae's survival is its ability to use available carbon sources. Here, we investigate the regulation of fruB, which encodes a protein central to the import and metabolism of fructose. We show that fruB expression is controlled by the transcriptional regulators Cra and CRP. This work contributes toward a clearer understanding of how carbon source availability impacts the physiology and, potentially, the persistence of the pathogen.

Cellular and Molecular Mechanisms Mediating Methylmercury Neurotoxicity and Neuroinflammation.

Methylmercury (MeHg) toxicity is a major environmental concern. In the aquatic reservoir, MeHg bioaccumulates along the food chain until it is consumed by riverine populations. There has been much interest in the neurotoxicity of MeHg due to recent environmental disasters. Studies have also addressed the implications of long-term MeHg exposure for humans. The central nervous system is particularly susceptible to the deleterious effects of MeHg, as evidenced by clinical symptoms and histopathological changes in poisoned humans. In vitro and in vivo studies have been crucial in deciphering the molecular mechanisms underlying MeHg-induced neurotoxicity. A collection of cellular and molecular alterations including cytokine release, oxidative stress, mitochondrial dysfunction, Ca2+ and glutamate dyshomeostasis, and cell death mechanisms are important consequences of brain cells exposure to MeHg. The purpose of this review is to organize an overview of the mercury cycle and MeHg poisoning events and to summarize data from cellular, animal, and human studies focusing on MeHg effects in neurons and glial cells. This review proposes an up-to-date compendium that will serve as a starting point for further studies and a consultation reference of published studies.

Amoebae can promote the survival of Francisella species in the aquatic environment

ABSTRACT Francisella tularensis, a tier 1 select agent, is the causative bacterium of tularemia, a zoonosis with a large animal reservoir. However, F. tularensis, like many other Francisella species, is assumed to have an aquatic reservoir. The mechanisms of Francisella species persistence in surface water remain poorly characterized. In this study, we deeply investigated the long-term interactions of the tularemia agent F. tularensis subsp. holarctica, F. novicida or F. philomiragia with amoebae of the Acanthamoeba species. In amoeba plate screening tests, all the Francisella species tested resisted the attack by amoebae. In in vitro infection models, intra-amoebic growth of Francisella varied according to the involved bacterial species and strains, but also the amoeba culture medium used. In co-culture models, the amoebae favoured Francisella survival over 16 days, which was likely dependent on direct contact between bacteria and amoebae for F. novicida and on amoeba-excreted compounds for F. novicida and for F. tularensis. In a spring water co-culture model, amoebae again enhanced F. novicida survival and preserved bacterial morphology. Overall, our results demonstrate that amoebae likely promote Francisella survival in aquatic environments, including the tularemia agent F. tularensis. However, bacteria-amoebae interactions are complex and depend on the Francisella species considered.

Microbial ecology: A new perspective of plastic degradation

Plastic pollution has emerged as an inevitable socio-environmental cause of pollution with ever increasing loads of plastic in everyday life. Extensive use of plastics especially disposable plastic (single-use) and presence of these non-degradable plastics in environment posing great menace to biodiversity in many habitats by disturbing ecosystem functioning. The purpose of this review is to explore the role of free living or symbiotic microbes in plastic degradation documented in the literature. Millions of plastic bags, dispensing containers, packaging and drinking bottles are thrown into the environment after single use every day. Polyethylene terephthalate (PET), Low density polyethylene (LDPE), Polypropylene (PP), Polystyrene (PS) and Expanded polystyrene (EPS) are major types of plastics used in the manufacture of millions of plastic bags, dispensing containers, packaging, food packaging film and drinking bottles are thrown into the environment after single use every day. These plastics accumulate in aquatic reservoirs and affects feeding guilds; ultimately disturbing community structure and ecosystem productivity. Five bacterial strains (belonging to genera Pseudomonas and Bacillus) have been isolated and found effective in degrading plastic. Recently, few insect larvae have been explored for their ability to feed on plastics; numerous bacterial strains, showing potential for degrading plastics, have been isolated from the guts of Tenebrio molitor, Tenebrio obscurus and Plodia interpunctella larvae. Biodegradation of plastics can prove to be an environment friendly way of eliminating plastics waste from environment. Elaborative work leading to the identification of specific enzymes and degradation pathways can help in plastic degradation at industrial level. Keywords: Biodegradation; Insect larvae; Microbial species; Microplastics http://dx.doi.org/10.19045/bspab.2020.90228

Validation of Hydrocharis morsus-ranae as a possible bioindicator of trace element pollution in freshwaters using Ceratophyllum demersum as a reference species.

The assessment of trace metal pollution in aquatic environments remains a challenge. Chemical methods are insufficient and bioindicators seem to be the most promising alternative. Finding an adequate species is important to ensure accurate data. The combined use of several bioindicators may help to overcome the limitations of species' spatial distribution and specific reactions. The aims of the present study were to compare the contents and bioaccumulation capability of 11 trace elements in Ceratophyllum demersum and different organs of Hydrocharis morsus-ranae and to validate H.morsus-ranae as a bioindicator of pollution in aquatic reservoirs using C.demersum, an established bioindicator, as a reference species. The application of several statistical techniques allowed us to identify similarities in accumulation patterns and concentration gradients between the two species. The results showed that concentrations of Cd, Co, Cr, Cu, Mn, Ni, Pb, Rb, Zn, V in C.demersum and roots of H.morsus-ranae were similar and mostly higher than in the leaves and stems of H.morsus-ranae. The contents of Cd, Co, Cr, Li, Mn, Ni, Rb, V, Zn were positively correlated. The inner transport of metals in H.morsus-ranae was limited (TF<1). Both species are accumulators (BF>103) of Ni and Zn, and H.morsus-ranae also of Cu and Pb. Frog-bit roots were chosen to be most promising in bioindication. Major axis regression analysis showed that the uptake of Cd, Cr, Co, Li and Pb was similar in the two species. Neural networks demonstrated substantial uniformity in responses of C.demersum and roots of H.morsus-ranae to the type of anthropogenic activity and land use and similar spatial distributions of Cd, Cr, Co, Li and Pb. When Nemerow Pollution Index was applied, both species showed congruent gradients of contamination. Thus, H.morsus-ranae was validated as a reliable bioindicator of trace metal pollution in freshwater.

Siderophore piracy enhances Vibrio cholerae environmental survival and pathogenesis.

Vibrio cholerae, the aetiological agent of cholera, possesses multiple iron acquisition systems, including those for the transport of siderophores. How these systems benefit V. cholerae in low-iron, polymicrobial communities in environmental settings or during infection remains poorly understood. Here, we demonstrate that in iron-limiting conditions, co-culture of V. cholerae with a number of individual siderophore-producing microbes significantly promoted V. cholerae growth in vitro. We further show that in the host environment with low iron, V. cholerae colonizes better in adult mice in the presence of the siderophore-producing commensal Escherichia coli. Taken together, our results suggest that in aquatic reservoirs or during infection, V. cholerae may overcome environmental and host iron restriction by hijacking siderophores from other microbes.