A biocoating confines nongrowing, metabolically active bacteria within a synthetic colloidal polymer (i.e., latex) film. Bacteria encapsulated inside biocoatings can perform useful functions, such as a biocatalyst in wastewater treatment. A biocoating needs to have a high permeability to allow a high rate of mass transfer for rehydration and the transport of both nutrients and metabolic products. It therefore requires an interconnected porous structure. Tuning the porosity architecture is a challenge. Here, we exploited rigid tubular nanoclays (halloysite) and nontoxic latex particles (with a relatively high glass transition temperature) as the colloidal "building blocks" to tailor the porosity inside biocoatings containing Escherichia coli bacteria as a model organism. Electron microscope images revealed inefficient packing of the rigid nanotubes and proved the existence of nanovoids along the halloysite/polymer interfaces. Single-cell observations using confocal laser scanning microscopy provided evidence for metabolic activity of the E. coli within the biocoatings through the expression of a yellow fluorescent protein. A custom-built apparatus was used to measure the permeability of a fluorescein sodium salt in the biocoatings. Whereas there was no measurable permeability in a coating made from only latex particles, the permeability coefficient of the composite biocoatings increased with increasing halloysite content up to a value of 1 × 10 −4 m h −1 . The effects of this increase in permeability was demonstrated through a specially developed resazurin reduction assay. Bacteria encapsulated in halloysite composite biocoatings had statistically significant higher metabolic activities in comparison to bacteria encapsulated in a nonoptimized coating made from latex particles alone.

Microbiological contamination of food during preparation and storage is a risk factor in institutional kitchens. In this Belgian study, hygiene practices in 40 institutional kitchens from four public sectors (10 hospitals, 10 schools, 10 retirement homes, and 10 child care centers) were evaluated to determine whether differences in these practices exist between these sectors. Contamination levels were also analyzed at several critical contact points. A data collection instrument and microbiological analysis of hand contact surfaces, food contact surfaces, and kitchen utensils were used. Hand washing resulted in only a slight reduction in total aerobic bacteria counts (TACs), and all microorganisms evaluated except E. coli were still present at countable levels. Enterobacteriaceae were found on one-third of the cleaned cutting boards. Cleaned work surfaces had the highest average TAC of all cleaned surfaces. Only slight improvements in TACs and Enterobacteriaceae and B. cereus counts were observed between used and cleaned work surfaces. The results from the data collection instrument revealed that child care centers had the lowest hygiene scores, whereas the other three sectors were fairly similar, with hospitals scoring highest. The low hygiene score for the child care centers was verified by comparing the results for cleaned surfaces among the sectors. The average TAC on surfaces was highest for child care centers and lowest for hospitals. Child care centers also had the second highest total mean counts and the highest number of total surface samples positive for Enterobacteriaceae. The highest number of surface samples positive for Staphylococcus aureus was also found in child care centers. This study highlights some areas of concern for hygiene improvement in institutional kitchens, differences between public sectors, and similarities in conclusions about hygiene based on the scores from the survey instrument and the results of the microbiological analyses. HIGHLIGHTS

Biofilm bioreactors are attracting growing interest in the wastewater industry, as they allow higher cell densities and thus higher reaction rates compared to conventional bioreactors. However, some commonly used nitrifying bacteria, such as Nitrosomonas europaea, are slow‐growing and need a prolonged period of time to develop a mature biofilm. Here, a biocoating or “living paint” is introduced, which is a synthetic biofilm made from a colloidal polymer (synthetic latex) binder encapsulating viable nitrifying bacteria at high density. Conventionally, the film formation of biocoatings is achieved by drying a bacteria/latex mixture. However, this fabrication is detrimental to the viability of the encapsulated bacteria because of the osmotic stress induced by desiccation. A nondesiccating film formation process is presented for biocoatings, which exploits two colloid science phenomena: coagulation and wet sintering. Desiccation‐sensitive, nitrifying bacteria are employed in the biocoatings to convert NH4+ to NO2− and then NO3−. These biocoatings have a conversion rate (NO2− and NO3− production) of 3 mg N g−1 d−1 that is five times higher than in conventionally desiccated biocoatings. The reactivity continues over a period of 1 month. The processing method for these living paints is transformative for wastewater treatment and other applications using delicate, desiccation‐sensitive microorganisms.

Scientists still wonder if animal-derived microbes are prevalent in the environments of people who handle animals, especially when these microbes are suspected of being involved in human disease. The aim of this study was to test a local source tracking database by choosing an environment frequently used by veterinary students and veterinarians and by identifying resident microbiota composition and their sources of contamination (animals, environment, human beings…). The 16S rDNA amplicon sequencing was used to determine the bacterial taxonomic profiles of restroom surfaces. Bacterial sources were identified by linking our metadata-enriched local database to the microbiota profiling analysis using high-quality sequences. Microbiota profiling shows the dominance of four phyla: Actinobacteria, Bacteroidetes, Proteobacteria, and Firmicutes. If the restroom cleaning process did not appear to impact microbiota composition, significant differences regarding bacterial distribution were observed between men and women users in different sampling campaigns. Combining 16S rDNA profiling to our specific sources labeling pipeline we found aquatic and human origins sources were the primary environment keywords in our campaigns. The probable presence of known animal sources (bovids, insects, equids, suids…) associated with bacterial genera such as Chryseobacterium, Bergeyella, Fibrobacter, and Syntrophococcus was also involved in restroom surfaces, emphasizing the proximity between these restrooms and the exchange of bacteria between people involved in animals handling. To summarize, we have demonstrated that DNA sequence-based source tracking may be integrated with high-throughput bacterial community analysis to enrich microbial investigation of potential bacterial contamination sources especially for little known or poorly identified taxa. However, more research is needed to determine the tool's utility in other applications.

In this study, we aimed to develop a comprehensive microbial source amplicon database tailored for source tracking in veterinary settings. We rigorously tested our locally curated source tracking database by selecting a frequently accessed environment by veterinary students and veterinarians. By exploring the composition of resident microbiota and identifying potential sources of contamination, including animals, the environment, and human beings, we aimed to provide valuable insights into the dynamics of microbial transmission within veterinary facilities. The 16S rDNA amplicon sequencing was used to determine the bacterial taxonomic profiles of restroom surfaces. Bacterial sources were identified by linking our metadata-enriched local database to the microbiota profiling analysis using high-quality sequences. Microbiota profiling shows the dominance of four phyla: Actinobacteria, Bacteroidetes, Proteobacteria, and Firmicutes. If the restroom cleaning process did not appear to impact microbiota composition, significant differences regarding bacterial distribution were observed between male and female users in different sampling campaigns. Combining 16S rDNA profiling to our specific sources labeling pipeline, we found aquatic and human sources were the primary environment keywords in our campaigns. The probable presence of known animal sources (bovids, insects, equids, suids…) associated with bacterial genera such as Chryseobacterium, Bergeyella, Fibrobacter, and Syntrophococcus was also involved in restroom surfaces, emphasizing the proximity between these restrooms and the exchange of bacteria between people involved in animals handling. To summarize, we have demonstrated that DNA sequence-based source tracking may be integrated with high-throughput bacterial community analysis to enrich microbial investigation of potential bacterial contamination sources, especially for little known or poorly identified taxa. However, more research is needed to determine the tool’s utility in other applications.

Background: Biocoatings are nanoporous polymer materials which encapsulate bacterial cells with carbohydrates as osmoprotectants. Here, we optimised biocoatings to offer a favourable environment for the metabolic activity of bacteria. Methods: E. coli were used as a model organism and mixed with the colloidal polymer particles (i.e. synthetic latex), inorganic nanoparticles and different carbohydrates. Films were casted and dried to create a coalesced latex film and finally rehydrated to re-establish bacterial metabolism. The toxicity of the sterile latices to the bacteria was tested by using the colourimetric redox indicator resazurin. Visualisation of the bacteria inside the biocoatings was performed by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Results: We introduced halloysite (clay nanotubes) to create nanoporosity, which created voids in the structure that will permit gas exchange. The biocoatings were tested in liquid and rehydrated states with resazurin to find the most promising composition ensuring bacterial viability. Rehydrated biocoatings were visualised by CLSM by tracking the constitutively expressed yellow-fluorescent protein (YFP) for viable cells and the membrane exclusion dye propidium iodide for dead cells. The structure of the biocoatings appeared to be unaffected by freeze-drying compared to chemical fixation. Following this fixation, SEM allowed the observation of the organisation of the latex polymers, halloysite and bacteria. Conclusions: The biocoatings were highly porous thanks to halloysite. E. coli survived the film formation process. Next, we will use E. coli and cyanobacteria to achieve higher efficiency for a variety of applications e.g. pollutant degradation, solar energy harvesting and carbon recycling.