Physicochemical analysis of initial adhesion and biofilm formation of Methanosarcina barkeri on polymer support material.

The retention of selective biofilms of Methanosarcina species within anaerobic digesters could reduce start-up times and enhance the efficiency of the process in treating high-strength domestic sewage. The objective of the study was to examine the effect of the surface characteristics of six common polymer support materials on the initial adhesion of the model methanogen, Methanosarcina barkeri, and to assess the potential of these support materials as selective biofilm carriers. Results from both the initial adhesion tests and extended DLVO (xDLVO) model correlated with each other, with PVC (12% surface coverage/mm(2)), PTFE (6% surface coverage/mm(2)), and PP (6% surface coverage/mm(2)), shown to be the better performing support materials for initial adhesion, as well as subsequent biofilm formation by M. barkeri after 72h. Experimental results of these three support materials showed that the type of material strongly influenced the extent of adhesion from M. barkeri (p<0.0001), and the xDLVO model was able to explain the results in these environmental conditions. Therefore, DLVO physicochemical forces were found to be influential on the initial adhesion of M. barkeri. Scanning electron microscopy suggested that production of extracellular polymeric substances (EPS) from M. barkeri could facilitate further biofilm development. This study highlights the potential of using the xDLVO model to rapidly identify suitable materials for the selective adhesion of M. barkeri, which could be beneficial in both the start-up and long-term phases of anaerobic digestion

Biodesalination: an emerging technology for targeted removal of Na+and Cl−from seawater by cyanobacteria

Although desalination by membrane processes is a possible solution to the problem of freshwater supply, related cost and energy demands prohibit its use on a global scale. Hence, there is an emerging necessity for alternative, energy and cost-efficient methods for water desalination. Cyanobacteria are oxygen-producing, photosynthetic bacteria that actively grow in vast blooms both in fresh and seawater bodies. Moreover, cyanobacteria can grow with minimal nutrient requirements and under natural sunlight. Taking these observations together, a consortium of five British Universities was formed to test the principle of using cyanobacteria as ion exchangers, for the specific removal of Na+ and Cl− from seawater. This project consisted of the isolation and characterisation of candidate strains, with central focus on their potential to be osmotically and ionically adaptable. The selection panel resulted in the identification of two Euryhaline strains, one of freshwater (Synechocystis sp. Strain PCC 6803) and one of marine origin (Synechococcus sp. Strain PCC 7002) (Robert Gordon University, Aberdeen). Other work packages were as follows. Genetic manipulations potentially allowed for the expression of a light-driven, Cl−-selective pump in both strains, therefore, enhancing the bioaccumulation of specific ions within the cell (University of Glasgow). Characterisation of surface properties under different salinities (University of Sheffield), ensured that cell–liquid separation efficiency would be maximised post-treatment, as well as monitoring the secretion of mucopolysaccharides in the medium during cell growth. Work at Newcastle University is focused on the social acceptance of this scenario, together with an assessment of the potential risks through the generation and application of a Hazard Analysis and Critical Control Points plan. Finally, researchers in Imperial College (London) designed the process, from biomass production to water treatment and generation of a model photobioreactor. This multimodal approach has produced promising first results, and further optimisation is expected to result in mass scaling of this process

Adapting the algal microbiome for growth on domestic landfill leachate

We aimed to improve algal growth rate on leachate by optimising the algal microbiome. An algal-bacterial consortium was enriched from landfill leachate and subjected to 24 months of adaptive laboratory evolution, increasing the growth rate of the dominant algal strain, Chlorella vulgaris, almost three-fold to 0.2 d^−1. A dramatic reduction in nitrate production suggested a shift in biological utilisation of ammoniacal-N, supported by molecular 16S rRNA taxonomic analyses, where Nitrosomonas numbers were not detected in the adapted consortium. A PICRUSt approach predicted metagenomic functional content and revealed a high number of sequences belonging to bioremediation pathways, including degradation of aromatic compounds, benzoate and naphthalene, as well as pathways known to be involved in algal-bacterial symbiosis. This study enhances our understanding of beneficial mechanisms in algal-bacterial associations in complex effluents, and ultimately enables the bottom-up design of optimised algal microbiomes for exploitation within industry

A novel high-throughput ex vivo ovine skin wound model for testing emerging antibiotics

The development of antimicrobials is an expensive process with increasingly low success rates, which makes further investment in antimicrobial discovery research less attractive. Antimicrobial drug discovery and subsequent commercialization can be made more lucrative if a fail-fast-and-fail-cheap approach can be implemented within the lead optimization stages where researchers have greater control over drug design and formulation. In this article, the setup of an ex vivo ovine wounded skin model infected with Staphylococcus aureus is described, which is simple, cost-effective, high throughput, and reproducible. The bacterial physiology in the model mimics that during infection as bacterial proliferation is dependent on the pathogen's ability to damage the tissue. The establishment of wound infection is verified by an increase in viable bacterial counts compared to the inoculum. This model can be used as a platform to test the efficacy of emerging antimicrobials in the lead optimization stage. It can be contended that the availability of this model will provide researchers developing antimicrobials with a fail-fast-and-fail-cheap model, which will help increase success rates in subsequent animal trials. The model will also facilitate the reduction and refinement of animal use for research and ultimately enable faster and more cost-effective translation of novel antimicrobials for skin and soft tissue infections to the clinic

Dokaz vrsta B. canis vogeli, B. gibsoni i E. canis višestrukim PCR-om u prirodno inficiranih pasa u Južnoj Indiji

Tick borne haemoparasites and haemorickettsiales pose a major health risk to animals worldwide. The present study reports the development and validation of multiplex PCR to simultaneously detect the most prevalent tick borne pathogens infecting dogs in Kerala, South India. The assay targeting the small subunit ribosomal RNA genes of the organisms could amplify well demarcated amplicons of B. canis vogeli, B. gibsoni and E. canis. In the study population, which included both healthy dogs as well as those with clinical symptoms suggestive of the three infections under study, 46.6% animals were infected with one of the three pathogens, amongst which the occurrence of B. gibsoni was significantly the highest. Natural co-infections were also detected in nine dogs, which suggests the suitability of the assay to assist in the selection of pathogen specific treatment protocols.Krvni paraziti i rikecije podrijetlom iz krpelja glavna su opasnost za zdravlje životinja diljem svijeta. U ovom je istraživanju razvijen i validiran višestruki PCR za istodobno dokazivanje najčešćih uzročnika koje na pse prenose krpelji u Kerali u Južnoj Indiji. Malim ciljnim subjediničnim ribosomskim RNA mogli su proizvesti jasno razlučivi produkti specifični za B. canis vogeli, B. gibsoni i E. canis. U pretraživanoj populaciji koja je obuhvaćala zdrave pse i one s kliničkim znakovima, koji su upućivali na infekciju uzrokovanu jednim od spomenutih uzročnika, 46,6 % životinja bilo je inficirano jednim od njih triju. Infekcija vrstom B. gibsoni bila je znatno češća. Prirodna je koinfekcija dokazana u devet pasa, što potvrđuje prikladnost testa za dijagnostiku i njegovo značenje pri poduzimanju odgovarajućeg liječenja

Influence of phosphate dosing on biofilms development on lead in chlorinated drinking water bioreactors

Phosphate dosing is used by water utilities to prevent plumbosolvency in water supply networks. However, there is a lack of knowledge regarding biofilm formation on lead and plastic materials when phosphate concentrations are modified in drinking water systems. In this study, biofilms were grown over lead coupons and PVC tubes in bioreactors supplied with local drinking water treated to provide different phosphate doses (below 1, 1 and 2 mg/L) over a period of 28 days. A range of commercial iron pellets (GEH104 and WARP) were tested aiming to maintain phosphate levels below the average 1 mg/L found in drinking water. Changes in biofilm community structure in response to three different phosphate treatments were characterised by Illumina sequencing of the 16S rRNA gene for bacteria and the ITS2 gene for fungi. Scanning electron microscopy was used to visualise physical differences in biofilm development in two types of materials, lead and PVC. The experimental results from the kinetics of phosphate absorption showed that the GEH104 pellets were the best option to, in the long term, reduce phosphate levels while preventing undesirable turbidity increases in drinking water. Phosphate-enrichment promoted a reduction of bacterial diversity but increased that of fungi in biofilms. Overall, higher phosphate levels selected for microorganisms with enhanced capabilities related to phosphorus metabolism and heavy metal resistance. This research brings new insights regarding the influence of different phosphate concentrations on mixed-species biofilms formation and drinking water quality, which are relevant to inform best management practices in drinking water treatment

Metabolic insights into infochemicals induced colony formation and flocculation in scenedesmus subspicatus unraveled by quantitative proteomics

Microalgae can respond to natural cues from crustacean grazers, such as Daphnia, by forming colonies and aggregations called flocs. Combining microalgal biology, physiological ecology, and quantitative proteomics, we identified how infochemicals from Daphnia trigger physiological and cellular level changes in the microalga Scenedesmus subspicatus, underpinning colony formation and flocculation. We discovered that flocculation occurs at an energy-demanding ‘alarm’ phase, with an important role proposed in cysteine synthesis. Flocculation appeared to be initially stimulated by the production of an extracellular matrix where polysaccharides and fatty acids were present, and later sustained at an ‘acclimation’ stage through mitogen-activated protein kinase (MAPK) signaling cascades. Colony formation required investment into fatty acid metabolism, likely linked to separation of membranes during cell division. Higher energy demands were required at the alarm phase, which subsequently decreased at the acclimation stage, thus suggesting a trade-off between colony formation and flocculation. From an ecological and evolutionary perspective, our findings represent an improved understanding of the effect of infochemicals on microalgae-grazers interactions, and how they can therefore potentially impact on the structure of aquatic communities. Moreover, the mechanisms revealed are of interest in algal biotechnology, for exploitation in low-cost, sustainable microalgal biomass harvesting

Characterization of ocular clinical isolates of Pseudomonas aeruginosa from non-contact lens related keratitis patients from south India

P. aeruginosa is the most common Gram-negative organism causing bacterial keratitis. Pseudomonas utilizes various virulence mechanisms to adhere and colonize in the host tissue. In the present study, we examined virulence factors associated with thirty-four clinical P. aeruginosa isolates collected from keratitis patients seeking care at L V Prasad Eye Institute, Hyderabad. The virulence-associated genes in all the isolates were genotyped and characteristics such as antibiotic susceptibility, biofilm formation, swarming motility, pyoverdine production and cell cytotoxicity were analyzed. All the isolates showed the presence of genes related to biofilm formation, alkaline proteases and elastases; however, there was a difference in the presence of genes related to the type III secretion system (T3SS). A higher prevalence of exoU+ genotype was noted in the drug-resistant isolates. All the isolates were capable of forming biofilms and more than 70% of the isolates showed good swarming motility. Pyoverdine production was not associated with the T3SS genotype. In the cytotoxicity assay, the presence of exoS, exoU or both resulted in higher cytotoxicity compared to the absence of both the genes. Overall, our results suggest that the T3SS profile is a good indicator of P. aeruginosa virulence characteristics and the isolates lacking the effector genes may have evolved alternate mechanisms of colonization in the host

Corneal infection models : tools to investigate the role of biofilms in bacterial keratitis

Bacterial keratitis is a corneal infection which may cause visual impairment or even loss of the infected eye. It remains a major cause of blindness in the developing world. Staphylococcus aureus and Pseudomonas aeruginosa are common causative agents and these bacterial species are known to colonise the corneal surface as biofilm populations. Biofilms are complex bacterial communities encased in an extracellular polymeric matrix and are notoriously difficult to eradicate once established. Biofilm bacteria exhibit different phenotypic characteristics from their planktonic counterparts, including an increased resistance to antibiotics and the host immune response. Therefore, understanding the role of biofilms will be essential in the development of new ophthalmic antimicrobials. A brief overview of biofilm-specific resistance mechanisms is provided, but this is a highly multifactorial and rapidly expanding field that warrants further research. Progression in this field is dependent on the development of suitable biofilm models that acknowledge the complexity of the ocular environment. Abiotic models of biofilm formation (where biofilms are studied on non-living surfaces) currently dominate the literature, but co-culture infection models are beginning to emerge. In vitro, ex vivo and in vivo corneal infection models have now been reported which use a variety of different experimental techniques and animal models. In this review, we will discuss existing corneal infection models and their application in the study of biofilms and host-pathogen interactions at the corneal surface