Flow cytometry for immediate follow-up of drinking water networks after maintenance.

Drinking water networks need maintenance every once in a while, either planned interventions or emergency repairs. When this involves opening of the water pipes, precautionary measures need to be taken to avoid contamination of the drinking water at all time. Drinking water suppliers routinely apply plating for faecal indicator organisms as quality control in such a situation.

The more, the merrier: heterotroph richness stimulates methanotrophic activity.

Although microorganisms coexist in the same environment, it is still unclear how their interaction regulates ecosystem functioning. Using a methanotroph as a model microorganism, we determined how methane oxidation responds to heterotroph diversity. Artificial communities comprising of a methanotroph and increasing heterotroph richness, while holding equal starting cell numbers were assembled.

Synthetic microbial ecosystems: an exciting tool to understand and apply microbial communities.

Many microbial ecologists have described the composition of microbial communities in a plenitude of environments, which has greatly improved our basic understanding of microorganisms and ecosystems. However, the factors and processes that influence the behaviour and functionality of an ecosystem largely remain black boxes when using conventional approaches. Therefore, synthetic microbial ecology has gained a lot of interest in the last few years.

Bacterial invasion potential in water is determined by nutrient availability and the indigenous community.

In drinking water (DW) and the distribution systems, bacterial growth and biofilm formation have to be controlled both for limiting taste or odour development and preventing clogging or biocorrosion problems. After a contamination with undesired bacteria, factors like nutrient availability and temperature will influence the survival of these invaders. Understanding the conditions enabling invaders to proliferate is essential for a holistic approach towards microbial risk assessment in DW.

Biofilm-grown Burkholderia cepacia complex cells survive antibiotic treatment by avoiding production of reactive oxygen species.

The presence of persister cells has been proposed as a factor in biofilm resilience. In the present study we investigated whether persister cells are present in Burkholderia cepacia complex (Bcc) biofilms, what the molecular basis of antimicrobial tolerance in Bcc persisters is, and how persisters can be eradicated from Bcc biofilms. After treatment of Bcc biofilms with high concentrations of various antibiotics often a small subpopulation survived.

Environmental conditions and community evenness determine the outcome of biological invasion.

Biological invasion is widely studied, however, conclusions on the outcome of this process mainly originate from observations in systems that leave a large number of experimental variables uncontrolled. Here using a fully controlled system consisting of assembled bacterial communities, we evaluate the degree of invasion and the effect on the community functionality in relation to the initial community evenness under specific environmental stressors. We show that evenness influences the level of invasion and that the introduced species can promote functionality under stress.

Comparing metabolic functionalities, community structures, and dynamics of herbicide-degrading communities cultivated with different substrate concentrations.

Two 4-chloro-2-methylphenoxyacetic acid (MCPA)-degrading enrichment cultures selected from an aquifer on low (0.1 mg liter(-1)) or high (25 mg liter(-1)) MCPA concentrations were compared in terms of metabolic activity, community composition, population growth, and single cell physiology. Different community compositions and major shifts in community structure following exposure to different MCPA concentrations were observed using both 16S rRNA gene denaturing gradient gel electrophoresis fingerprinting and pyrosequencing.

The use of liposomes to differentiate between the effects of nickel accumulation and altered food quality in Daphnia magna exposed to dietary nickel.

A potential drawback of traditional dietary metal toxicity studies is that it is difficult to distinguish between the direct toxicity of the metal and indirect effects caused by altered concentrations of essential nutrients in the metal-contaminated diet. In previous studies it has become clear that this can hamper the study of the real impact of dietary metal exposure and also complicates the analysis of the mechanisms of dietary metal toxicity in filter-feeding freshwater invertebrates like Daphnia magna. This problem has been partly circumvented by the production of liposomes, since these vectors are invulnerable to metal-induced food quality shifts and as such can be applied to study the mechanisms of dietary metal toxicity without the confounding effect of nutritional quality shifts.

Flow cytometry for fast microbial community fingerprinting.

Characterizing the microbial community of water is important in different domains, ranging from food and beverage production to wastewater treatment. Conventional methods, such as heterotrophic plate count, selective plating and molecular techniques, are time consuming and labor intensive. A flow cytometry based approach was developed for a fast and objective comparison of microbial communities based on the distribution of cellular features from single cells within these communities.

Liposomes as an alternative delivery system for investigating dietary metal toxicity to Daphnia magna.

Dietary metal toxicity studies with invertebrates such as Daphnia magna are often performed using metal-contaminated algae as a food source. A drawback of this approach is that it is difficult to distinguish between the direct toxicity of the metal and indirect effects caused by a reduced essential nutrient content in the metal-contaminated diet, due to prior exposure of the algae to the metal. This hampers the study of the mechanisms of dietary metal toxicity in filter-feeding freshwater invertebrates.

Past, present and future applications of flow cytometry in aquatic microbiology.

Flow cytometry (FCM) is rapidly becoming an essential tool in the field of aquatic microbiology. It provides opportunities for microbial analysis at both the community and single-cell levels. Compared with other techniques, FCM facilitates rapid data acquisition and multi-parameter analysis, leading to increased popularity and widespread applications.