Bacterial Diversity In Biofilms Research Articles

Handwashing basins and healthcare associated infections: Bacterial diversity in biofilms on faucets and drains

BackgroundIncreasingly, hospital handwashing basins have been identified as a source of healthcare-associated infections. Biofilms formed on the faucet and drains of handbasins can potentially harbour pathogenic microbes and promote the dissemination of antimicrobial resistance. However, little is known about the diversity of these biofilm communities and the routes of contamination. AimThe aim of this paper was to use 16S rRNA gene amplicon sequencing to investigate the diversity of prokaryote communities present in faucet and drain biofilm samples taken from hospital and residential handbasins. FindingsThe biofilm prokaryotes communities were diverse, with high abundances of potentially corrosive, biofilm forming and pathogenic genera, including those that are not typically waterborne. The β-diversity showed statistically significant differences in the variation of bacterial communities on the basis on building type (hospital vs residential p = 0.0415). However, there was no statistically significant clustering based on sampling site (faucet vs drain p = 0.46). When examining the β-diversity between individual factors, there was a significant difference between drain biofilms of different buildings (hospital drain vs residential drain p = 0.0338). ConclusionThis study demonstrated that biofilms from hospital and residential handbasins contain complex and diverse microbial communities that differ significantly by building type. It also showed biofilms formed on the faucet and drain of a hospital's handbasins were not significantly different. Future research is needed to understand the potential mechanisms of transfer between drains and faucets of hospital handbasins. This information will inform improved infection control guidelines to control this underrecognized source of infections.

Characterization of bacterial biofilms developed on the biodegradable polylactide and polycaprolactone polymers containing birch tar in an aquatic environment

Birch tar was added to polylactide (PLA) and polycaprolactone (PCL) to create films with antimicrobial properties. After incubating the films for seven days in lake water, the diversity of bacterial communities developed on the surfaces of PCL and PLA with embedded birch tar (1 %, 5 %, and 10 %, w/w) was assessed with amplicon sequencing of the 16S rRNA gene on a MiSeq platform (Illumina). Notably, Aquabacterium and Caulobacter were more abundant at the surface of PCL compared to PLA (13.4 % vs 0.2 %, p < 0.001 and 9.5 % vs 0.2 %, p < 0.001, respectively) while Hydrogenophaga was significantly more abundant at the surface of PLA compared to PCL (6.1 % vs 1.8 %, p < 0.01). Overall, lower birch tar concentrations (1 % and 5 % on both polymers) stimulated bacterial diversity in biofilms compared to the control. The number of reeds assigned to Flavobacterium and Aquabacterium showed a rising trend with the increase of birch tar concentration on the surface of both polymers.

Bacterial diversity of biofilms on polyhydroxybutyrate exposed to marine conditions: Ex-situ vs. in-situ tests

Biofilms form on any available surface and, depending on the characteristics of the material and the environmental conditions, biodegradation can take place. We compared the bacterial composition of polyhydroxybutyrate (PHB)-related biofilm communities from marine ex-situ and in-situ tests to assess the differences in diversity and abundance between these two biofilms. This comparison will help to better assess the transferability of tank tests to real-life scenarios. The in-situ tests were set up in the Mediterranean Sea on the Island of Elba, Italy where PHB-tensile bars were lodged in the sediments. This created a water-exposed aerobic and mud-planted anaerobic scenario. The ex-situ tests were modeled after in-situ tests and performed in temperature-controlled tanks. The PHB-related biofilms were harvested after 240 days of exposure along with planktonic bacteria, and particle- and sediment-related biofilm. The bacterial composition was elucidated using 16S rDNA sequencing. Biofilms harvested from the in-situ test were more diverse, less even, and contained more rare species compared to biofilms from the ex-situ test. The PHB-related biofilm was characterized by a higher abundance of the bacterial order Desulfobacterales. The composition of PHB-related biofilm varied significantly between the two tests and between aerobic and anaerobic conditions. The composition of PHB-related biofilm was significantly different from planktonic bacteria, particle, and sediment-related biofilm, showing the influence of PHB on the biofilm composition. Thus, the ex-situ tank test for PHB degradation cannot, in terms of bacterial composition, simulate the in-situ conditions to their full extent.

Microbial Diversity and Putative Opportunistic Pathogens in Dishwasher Biofilm Communities.

ABSTRACTExtreme habitats are not only limited to natural environments, but also exist in manmade systems, for instance, household appliances such as dishwashers. Limiting factors, such as high temperatures, high and low pHs, high NaCl concentrations, presence of detergents, and shear force from water during washing cycles, define microbial survival in this extreme system. Fungal and bacterial diversity in biofilms isolated from rubber seals of 24 different household dishwashers was investigated using next-generation sequencing. Bacterial genera such as Pseudomonas, Escherichia, and Acinetobacter, known to include opportunistic pathogens, were represented in most samples. The most frequently encountered fungal genera in these samples belonged to Candida, Cryptococcus, and Rhodotorula, also known to include opportunistic pathogenic representatives. This study showed how specific conditions of the dishwashers impact the abundance of microbial groups and investigated the interkingdom and intrakingdom interactions that shape these biofilms. The age, usage frequency, and hardness of incoming tap water of dishwashers had significant impact on bacterial and fungal community compositions. Representatives of Candida spp. were found at the highest prevalence (100%) in all dishwashers and are assumed to be one of the first colonizers in recently purchased dishwashers. Pairwise correlations in tested microbiomes showed that certain bacterial groups cooccur, as did the fungal groups. In mixed bacterial-fungal biofilms, early adhesion, contact, and interactions were vital in the process of biofilm formation, where mixed complexes of bacteria and fungi could provide a preliminary biogenic structure for the establishment of these biofilms.IMPORTANCE Worldwide demand for household appliances, such as dishwashers and washing machines, is increasing, as is the number of immunocompromised individuals. The harsh conditions in household dishwashers should prevent the growth of most microorganisms. However, our research shows that persisting polyextremotolerant groups of microorganisms in household appliances are well established under these unfavorable conditions and supported by the biofilm mode of growth. The significance of our research is in identifying the microbial composition of biofilms formed on dishwasher rubber seals, how diverse abiotic conditions affect microbiota, and which key microbial members were represented in early colonization and contamination of dishwashers, as these appliances can present a source of domestic cross-contamination that leads to broader medical impacts.

Effects of water flow on submerged macrophyte-biofilm systems in constructed wetlands

The effects of water flow on the leaf-biofilm interface of Vallisneria natans and Hydrilla verticillata were investigated using artificial plants as the control. Water flow inhibited the growth of two species of submerged macrophytes, reduced oxygen concentrations in plant leaves and changed oxygen profiles at the leaf-biofilm interface. The results from confocal laser scanning microscopy and multifractal analysis showed that water flow reduced biofilm thickness, changed biofilm topographic characterization and increased the percentages of single colony-like biofilm patches. A cluster analysis revealed that the bacterial compositions in biofilms were determined mainly by substrate types and were different from those in sediments. However, water flow increased the bacterial diversity in biofilms in terms of operational taxonomic unit numbers and Shannon Indices. Our results indicated that water flow can be used to regulate the biomass, distribution and bacterial diversities of epiphytic biofilms in constructed wetlands dominated by submerged macrophytes.

Characterization of Microbial Signatures From Advanced Treated Wastewater Biofilms

Next‐generation sequencing (NGS) and metagenomics were used to identify microbial communities in biofilms of microfiltration (MF) and reverse osmosis (RO) membranes in an advanced water purification facility (AWPF) that treats municipal wastewater to produce potable quality water. Secondary treated wastewater effluent is the source of influent to the AWPF treatment train and was also characterized by NGS. Results show low bacterial diversity in biofilms obtained from the feed‐side surfaces of MF and RO membranes. Microbial communities and antibiotic resistance genes (ARGs) in the RO biofilm were compared with those of the MF and influent, revealing lower abundance of bacterial species and ARGs in the RO biofilm than in the other samples. Opportunistic pathogens were detected in all samples; however, indicator bacteria, viruses, and bacteriophages were not detected in the RO biofilm. It is concluded that NGS has great potential for improved detection and characterization of microbial communities in biofilms that form on AWPF MF and RO membranes.

Improvements on colony morphology identification towards bacterial profiling

Colony morphology may be an indicator of phenotypic variation, this being an important adaptive process adopted by bacteria to overcome environmental stressors. Furthermore, alterations in colony traits may reflect increased virulence and antimicrobial resistance. Despite the potential relevance of using colony morphological traits, the influence of experimental conditions on colony morphogenesis has been scarcely studied in detail. This study aims to clearly and systematically demonstrate the impact of some variables, such as colony growth time, plate colony density, culture medium, planktonic or biofilm mode of growth and strain genetic background, on bacterial colony morphology features using two Pseudomonas aeruginosa strains. Results, based on 5-replicate experiments, demonstrated that all variables influenced colony morphogenesis and 18 different morphotypes were identified, showing different sizes, forms, colours, textures and margins. Colony growth time and composition of the medium were the variables that caused the highest impact on colony differentiation both derived from planktonic and biofilm cultures. Colony morphology characterization before 45h of incubation was considered inadequate and TSA, a non-selective medium, provided more colony diversity in contrast to P. aeruginosa selective media. In conclusion, data obtained emphasized the need to perform comparisons between colony morphologies in equivalent experimental conditions to avoid misinterpretation of microbial diagnostics and biomedical studies. Since colony morphotyping showed to be a reliable method to evaluate phenotypic switching and also to infer about bacterial diversity in biofilms, these unambiguous comparisons between morphotypes may offer a quite valuable input to clinical diagnosis, aiding the decision-making towards the selection of the most suitable antibiotic and supportive treatments.

Diversity of bacteria and mycobacteria in biofilms of two urban drinking water distribution systems

In this study, to give insight into the bacterial diversity of biofilms from full-scale drinking water distribution systems (DWDSs), the bacterial community compositions of biofilms from two urban DWDSs (Guangzhou and Beijing, China) were determined using a 16S rRNA gene library technique. Meanwhile, the occurrence and diversity of mycobacteria were also analyzed by a Mycobacterium -specific hsp gene assay. The biofilms from the full-scale DWDSs have complex bacterial populations. Proteobacteria was the common and predominant group in all biofilm samples, in agreement with previous reports. The community structures of bacteria at the three sites in Guangzhou DWDS were significantly different, despite the similar physicochemical properties of portable water. Some abundant and peculiar bacterial phylotypes were noteworthy, including Methylophilus , Massilia, and Planomicrobium , members of which are rarely found in DWDSs and their roles in DWDS biofilms are still unclear. The diversity of Mycobacterium species in biofilm samples was rather low. Mycobacterium arupense and Mycobacterium gordonae were the primary Mycobacterium species in Guangzhou and Beijing biofilms, respectively, indicating that M. arupense may be more resistant to chloride than M. gordonae.

Bacterial diversity in biofilms formed on condenser tube surfaces in a nuclear power plant

To elucidate the bacterial diversity in biofilms formed on a condenser tube from a nuclear power plant, 16S rRNA gene sequences were examined using a PCR-cloning-sequencing approach. Twelve operational taxonomic units were retrieved in the clone library, and the estimated species richness was low (13.2). Most of the clones (94.7%) were affiliated with α-Proteobacteria; Planctomycetes and γ-Proteobacteria were much rarer. Interestingly, except for one clone belonging to Pseudoalteromonas, most of the sequences displayed sequence similarities <97% of those of the closest type strains. Based on 16S rRNA phylogenetic analysis, most bacteria were assigned to novel taxa above the species level. The low species richness and unusual bacterial composition may be attributable to selective pressure from chlorine in the cooling water. To prevent or control bacterial biofilms in cooling circuits, additional studies of the physiology and ecology of these species will be essential.

Bacterial diversity in biofilms on external surfaces of historic buildings in Porto Alegre

Bacteria, along with other microorganisms, are present on and in rocks or historic stone monuments and can cause biodeterioration. Gram-positive bacteria, although present in lower numbers, are principally responsible for the damage caused. Four churches and the Vice-Governor’s office in Porto Alegre, all buildings of historic importance were studied, using traditional microbiological methods, with the aim of assessing the microdiversity on their external surfaces. A large number of microorganisms was found in each biofilm. Cell morphology varied at different points and with season. Most of the gram-positive bacteria were of the Bacillus genus, which are readily able to survive the dry conditions on these exposed surfaces. The isolates with the highest deteriorating ability, producing acids and surfactants with autoemulsifing power, were Bacillus isolates B4, B6 and B10 from Priest groups II, I and III, respectively. These were evaluated.