Biofilm Bacterial Communities Research Articles

Biofilm of petroleum-based and bio-based microplastics in seawater in response to Zn(II): Biofilm formation, community structure, and microbial function

Microplastic biofilms are novel vectors for the transport and spread of pathogenic and drug-resistant bacteria. With the increasing use of bio-based plastics, there is an urgent need to investigate the microbial colonization characteristics of these materials in seawater, particularly in comparison with conventional petroleum-based plastics. Furthermore, the effect of co-occurring contaminants, such as heavy metals, on the formation of microplastic biofilms and bacterial communities remains unclear. In this study, we compared the biofilm bacterial community structure of petroleum-based polyethylene (PE) and bio-based polylactic acid (PLA) in seawater under the influence of zinc ions (Zn2+). Our findings indicate that the biofilm on PLA microplastics in the late stage was impeded by the formation of a mildly acidic microenvironment resulting from the hydrolysis of the ester group on PLA. The PE surface had higher bacterial abundance and diversity, with a more intricate symbiotic pattern. The bacterial structures on the two types of microplastics were different; PE was more conducive to the colonization of anaerobic bacteria, whereas PLA was more favorable for the colonization of aerobic and acid-tolerant species. Furthermore, Zn increased the proportion of the dominant genera that could utilize microplastics as a carbon source, such as Alcanivorax and Nitratireductor. PLA had a greater propensity to harbor and disseminate pathogenic and drug-resistant bacteria, and Zn promoted the enrichment and spread of harmful bacteria such as, Pseudomonas and Clostridioides. Therefore, further research is essential to fully understand the potential environmental effects of bio-based microplastics and the role of heavy metals in the dynamics of bacterial colonization.

Innovative inbuilt moving bed biofilm reactor for nitrogen removal applied in household aquarium.

An innovative inbuilt moving bed biofilm reactor (MBBR) was created to protect fish from nitrogen in a household aquarium. During the 90 experimental days, the ammonia nitrogen (NH4+-N) concentration in the aquarium with the inbuilt MBBR was always below 0.5 mg/L, which would not threaten the fish. Concurrently, nitrite and nitrate nitrogen concentrations were always below 0.05 mg/L and 4.5 mg/L, respectively. However, the blank contrast aquarium accumulated 1.985 mg/L NH4+-N on the 16th day, which caused the fish to die. The suspended biofilms could achieve the specific NH4+-N removal rate of 45.43 g/m3/d. Biofilms presented sparsely with filamentous structures and showed certain degrees of roughness. The bacterial communities of the suspended biofilms and the sediment were statistically different (p < 0.05), reflected in denitrifying and nitrifying bacteria. In particular, the relative abundance of Nitrospira reached 1.4%, while the genus was barely found in sediments. The suspended biofilms showed potentials for nitrification function with the predicted sequence numbers of ammonia monooxygenase [1.14.99.39] and hydroxylamine dehydrogenase [EC:1.7.2.6] of 220 and 221, while the values of the sediment were only 5 and 1. This study created an efficient NH4+-N removal inbuilt MBBR for household aquariums and explored its mechanism to afford a basis for its utilization.

Glycolanguage of the oral microbiota.

The oral cavity harbors a diverse and dynamic bacterial biofilm community which is pivotal to oral health maintenance and, if turning dysbiotic, can contribute to various diseases. Glycans as unsurpassed carriers of biological information are participating in underlying processes that shape oral health and disease. Bacterial glycoinfrastructure-encompassing compounds as diverse as glycoproteins, lipopolysaccharides (LPSs), cell wall glycopolymers, and exopolysaccharides-is well known to influence bacterial fitness, with direct effects on bacterial physiology, immunogenicity, lifestyle, and interaction and colonization capabilities. Thus, understanding oral bacterias' glycoinfrastructure and encoded glycolanguage is key to elucidating their pathogenicity mechanisms and developing targeted strategies for therapeutic intervention. Driven by their known immunological role, most research in oral glycobiology has been directed onto LPSs, whereas, recently, glycoproteins have been gaining increased interest. This review draws a multifaceted picture of the glycolanguage, with a focus on glycoproteins, manifested in prominent oral bacteria, such as streptococci, Porphyromonas gingivalis, Tannerella forsythia, and Fusobacterium nucleatum. We first define the characteristics of the different glycoconjugate classes and then summarize the current status of knowledge of the structural diversity of glycoconjugates produced by oral bacteria, describe governing biosynthetic pathways, and list biological roles of these energetically costly compounds. Additionally, we highlight emerging research on the unraveling impact of oral glycoinfrastructure on dental caries, periodontitis, and systemic conditions. By integrating current knowledge and identifying knowledge gaps, this review underscores the importance of studying the glycolanguage oral bacteria speak to advance our understanding of oral microbiology and develop novel antimicrobials.

Oxygen-dependent biofilm dynamics in leaf decay: an in vitro analysis

Biofilms are important in the natural process of plant tissue degradation. However, fundamental knowledge of biofilm community structure and succession on decaying leaves under different oxygen conditions is limited. Here, we used 16S rRNA and ITS gene amplicon sequencing to investigate the composition, temporal dynamics, and community assembly processes of bacterial and fungal biofilms on decaying leaves in vitro. Leaves harvested from three plant species were immersed in lake water under aerobic and anaerobic conditions in vitro for three weeks. Biofilm-covered leaf samples were collected weekly and investigated by scanning electron microscopy. The results showed that community composition differed significantly between biofilm samples under aerobic and anaerobic conditions, though not among plant species. Over three weeks, a clear compositional shift of the bacterial and fungal biofilm communities was observed. The alpha diversity of prokaryotes increased over time in aerobic assays and decreased under anaerobic conditions. Oxygen availability and incubation time were found to be primary factors influencing the microbial diversity of biofilms on different decaying plant species in vitro. Null models suggest that stochastic processes governed the assembly of biofilm communities of decaying leaves in vitro in the early stages of biofilm formation and were further shaped by niche-associated factors.

Chitosan Membranes Stabilized with Varying Acyl Lengths Release Cis-2-Decenoic Acid and Bupivacaine at Controlled Rates and Inhibit Pathogenic Biofilm.

Adherence of complex bacterial biofilm communities to burned tissue creates a challenge for treatment, with infection causing 51% of burn victim deaths. This study evaluated the release of therapeutics from wound care biomaterials and their antimicrobial activity against pathogens Staphylococcus aureus, Acinetobacter baumannii, and Pseudomonas aeruginosa. Electrospun chitosan membranes (ESCMs) were fabricated and acylated with chain lengths ranging from 6-10 carbons then loaded with 0.15 mg of anti-biofilm agent, cis-2-decenoic acid (C2DA), and 0.5 mg of local anesthetic, bupivacaine. Combinations of therapeutics released from modified ESCMs at a cumulative amount of 45-70% of bupivacaine and less than 20% of C2DA. Results from bacterial studies suggest that this combination reduced biofilm 10-fold for S. aureus, 2-fold for Acinetobacter baumannii, and 2-3-fold for Pseudomonas aeruginosa by 24 hours. Additionally, dual loaded groups reduced planktonic Staphylococcus aureus ~4-fold by 24 hours as well as Acinetobacter baumannii ~3-fold by 48 hours. The combination of therapeutics used has a significant role in biofilm prevention for selected strains via direct contact or diffusion in aqueous solutions.

Seasonal variation and human impacts of the river biofilm bacterial communities in the Shiting River in southeastern China.

Bacterial communities in epilithic biofilm plays an important role in biogeochemistry processes in freshwater ecosystems. Nevertheless, our understanding of the geographical and seasonal variations of the composition of bacterial communities in the biofilm of gravels on river bed is still limited. Various anthropogenic activities also influence the biofilm bacteria in gravel rivers. By taking the Shiting River in the upper Yangtze River basinin Sichuan Province as an example, we studied the geographical and seasonal variations of epilithic bacteria and the impacts of weirs and other human activities (e.g., sewage pollution). The river has experienced severe degradation since the Ms 8.0 Wenchuan Earthquake, and weirs were constructed to prevent bed erosion.We collected epilithic biofilms samples at 17 sites along ~ 30km river reach of the Shiting River in the autumn of 2021 and the summer of 2022, respectively. We applied 16S rRNA gene high-throughput sequencing technology and Functional Annotation of Prokaryotic Taxa (FAPROTAX) to analyze the seasonal and biogeographic patterns and potential functions of the biofilm bacterial communities. The results showed that epilithic bacteria from the two surveys exhibited variation in community composition, bacterial diversity and potential functions. The bacteria samples collected in the autumn have much higher alpha diversity and richness than those collected in the summer. Bacterial richness and diversity were lower downstream of the weirs than upstream. Low diversity was observed at a sampling site influenced by sewage inflow, which contains high level of nitrogen-related chemicals.

Biofilms on plastic litter in an urban river: Community composition and activity vary by substrate type.

In aquatic ecosystems, plastic litter is a substrate for biofilms. Biofilms on plastic and natural surfaces share similar composition and activity, with some differences due to factors such as porosity. In freshwaters, most studies have examined biofilms on benthic substrates, while little research has compared the activity and composition of biofilms on buoyant plastic and natural surfaces. Additionally, the influence of substrate size and successional stage on biofilm composition has not been commonly assessed. We incubated three plastics of distinct textures that are buoyant in rivers, low-density polyethylene (rigid; 1.7 mm thick), low-density polyethylene film (flexible; 0.0254 mm thick), and foamed polystyrene (brittle; 6.5 mm thick), as well as wood substrates (untreated oak veneer; 0.6 mm thick) in the Chicago River. Each material was incubated at three sizes (1, 7.5, and 15 cm2 ). Substrates were incubated at 2-10 cm depths and removed weekly for 6 weeks. On each substrate we measured chlorophyll concentration, biofilm biomass, respiration, and flux of nitrogen gas. We sequenced 16S and 23S rRNA genes at Weeks 1, 3, and 6 to capture biofilm community composition across successional stages. Chlorophyll, biomass, and N2 flux were similar across substrates, but respiration was greater on wood than plastics. Bacterial and algal richness and diversity were highest on foam and wood compared to polyethylene substrates. Bacterial biofilm community composition was distinct between wood and plastic substrates, while the algal community was distinct on wood and foam, which were different from each other and polyethylene substrates. These results indicate that polymer properties influence biofilm alpha and beta diversity, which may affect transport and distribution of plastic pollution and associated microbes, as well as biogeochemical processes in urban rivers. This study provides valuable insights into the effects of substrate on biofilm characteristics, and the ecological impacts of plastic pollution on urban rivers. PRACTITIONER POINTS: Plastic physical and chemical properties act as forces of selection for biofilm. Biofilm activity was similar among three different types of plastic. Community composition between plastic and wood was different.

Type VI secretion system drives bacterial diversity and functions in multispecies biofilms

Type VI secretion system (T6SS) plays an essential role in interspecies interactions and provides an advantage for a strain with T6SS in multispecies biofilms. However, how T6SS drives the bacterial community structure and functions in multispecies biofilms still needs to be determined. Using gene deletion and Illumina sequencing technique, we estimated bacterial community responses in multispecies biofilms to T6SS by introducing T6SS-containing Pseudomonas putida KT2440. Results showed that the niche structure shifts of multispecies biofilms were remarkably higher in the presence of T6SS than in the absence of T6SS. The presence of T6SS significantly drove the variation in microbial composition, reduced the alpha-diversity of bacterial communities in multispecies biofilms, and separately decreased and increased the relative abundance of Proteobacteria and Bacteroidota. Co-occurrence network analysis with inferred putative bacterial interactions indicated that P. putida KT2440 mainly displayed strong negative associations with the genera of Psychrobacter, Cellvibrio, Stenotrophomonas, and Brevundimonas. Moreover, the function redundancy index of the bacterial community was strikingly higher in the presence of T6SS than in the absence of T6SS, regardless of whether relative abundances of bacterial taxa were inhibited or promoted. Remarkably, the increased metabolic network similarity with T6SS-containing P. putida KT2440 could enhance the antibacterial activity of P. putida KT2440 on other bacterial taxa. Our findings extend knowledge of microbial adaptation strategies to potential bacterial weapons and could contribute to predicting biodiversity loss and change in ecological functions caused by T6SS.

Stronger deterministic processes shape the plastisphere microbiota of biodegradable microplastics compared to non-biodegradable microplastics in farmland soil

Biodegradable plastic (BP) is anticipated to become one of the most important strategies to alleviate plastic pollution. However, the colonization and assemblage of bacterial communities in biodegradable microplastic (BMP) plastisphere in farming soil ecosystems is still little understood. We carried out a field experiment in farmland soil with three fertilization practices to ascertain the differences in the bacterial community assembly between BMP and non-BMP plastispheres. We found that substrate type was the key factor determining the diversity and structure of bacterial communities in biofilms, in comparison with fertilization practice. The bacterial alpha diversity of BMP plastispheres was significantly lower than those of non-BMP plastispheres (p < 0.05). Deterministic processes dominated the bacterial community assembly of microplastic plastispheres in the farmland soil. Higher contributions of deterministic processes were observed in BMP plastispheres than in non-BMP plastispheres. Additionally, bacterial co-occurrence networks on BMPs were simpler and more unstable than those on non-BMPs, and some microorganisms with potential for degradation were identified as key taxa in bacterial co-occurrence networks of microplastics. Together, our findings provide insight on the peculiarities of bacterial community assembly mechanism on BMPs and a scientific basis for the application and management of biodegradable plastics in the future.

Selective enrichment of bacteria and antibiotic resistance genes in microplastic biofilms and their potential hazards in coral reef ecosystems

Microplastics become hotspots for bacteria to trigger a series of ecological effects, but few studies have focused on the potential impacts of microplastic biofilms in coral reef ecosystems. Here, we measured the bacterial communities and antibiotic resistance genes (ARGs) in the seawater and microplastic biofilms. Results showed that microbial biofilms were formed on the surface of microplastics. The alpha diversity of the bacterial community in the microplastic biofilms was lower than that in the seawater, and the bacterial communities were distinct between the two. Further analysis revealed that several bacteria in the microplastic biofilms carried ARGs, and the proportion of which was correlated to the concentration of antibiotics in the seawater. Specifically, Vibrio was positively correlated to sul1 in the microplastic biofilms under higher concentrations of sulfonamides. Pathway analysis reflected significant overrepresentation of human disease related pathways in the bacterial community of microplastic biofilms. These results suggest that the microplastic biofilms could selectively enrich bacteria from the reef environments, causing the development of ARGs under antibiotic driving. This may pose a serious threat to coral reef ecosystems and human health. Our study provides new insights into the ecological impacts of microplastic biofilms in coral reef ecosystems.

The role of phages for microdiverse bacterial communities in proglacial stream biofilms

Viruses modulate the diversity and activity of microbial communities. However, little is known about their role for the structure of stream bacterial biofilm communities. Here, we present insights into the diversity and composition of viral communities in various streams draining three proglacial floodplains in Switzerland. Proglacial streams are characterized by extreme environmental conditions, including near-freezing temperatures and ultra-oligotrophy. These conditions select for few but well-adapted bacterial clades, which dominate biofilm communities and occupy niches via microdiversification. We used metagenomic sequencing to reveal a diverse biofilm viral assemblage in these streams. Across the different floodplains and streams, viral community composition was tightly coupled to that of the bacterial hosts, which was underscored by generally high host specificity. Combining predictions of phage-host interactions with auxiliary metabolic genes (AMGs), we identify specific AMGs shared by phages infecting microdiverse clade members. Our work provides a step towards a better understanding of the complex interactions among bacteria and phages in stream biofilm communities in general and streams influenced by glacier meltwaters and characterized by microdiversity in particular.

Submerged macrophyte promoted nitrogen removal function of biofilms in constructed wetland

Biofilm is one of the important factors affecting nitrogen removal in constructed wetlands (CWs). However, the impact of submerged macrophyte on nitrogen conversion of biofilms on leaf of submerged macrophyte and matrix remains poorly understood. In this study, the CWs with Vallisneria natans and with artificial plant were established to investigate the effects of submerged macrophyte on nitrogen conversion and the composition of nitrogen-converting bacteria in leaf and matrix biofilms under high ammonium nitrogen (NH4+-N) loading. The 16S rRNA sequencing method was employed to explore the changes in bacterial communities in biofilms in CWs. The results showed that average removal rates of total nitrogen and NH4+-N in CW with V. natans reached 71.38% and 82.08%, respectively, representing increases of 24.19% and 28.79% compared with the control with artificial plant. Scanning electron microscope images indicated that high NH4+-N damaged the leaf cells of V. natans, leading to the cellular content release and subsequent increases of aqueous total organic carbon. However, the specific surface area and carrier function of V. natans were unaffected within 25 days. As a natural source of organic matters, submerged macrophyte provided organic matters for bacterial growth in biofilms. Bacterial composition analysis revealed the predominance of phylum Proteobacteria in CW with V. natans. The numbers of nitrifiers and denitrifiers in leaf biofilms reached 1.66 × 105 cells/g and 1.05 × 107 cells/g, as well as 2.79 × 105 cells/g and 7.41 × 107 cells/g in matrix biofilms, respectively. Submerged macrophyte significantly increased the population of nitrogen-converting bacteria and enhanced the expressions of nitrification genes (amoA and hao) and denitrification genes (napA, nirS and nosZ) in both leaf and matrix biofilms. Therefore, our study emphasized the influence of submerged macrophyte on biofilm functions and provided a scientific basis for nitrogen removal of biofilms in CWs.

Enhanced electricity generation of a 1.2-L microbial fuel cell with acclimation of applied voltage

The aim of this study was to investigate the effect of acclimation at different applied voltages on the electricity generation and composition of anodic biofilm in microbial fuel cell (MFC). Single-chamber air-cathode 1.2-L MFCs were acclimated by different applied voltages (i.e., 0.5, 1.0, 1.5 and 2.0 V). The maximum power density of 1587 mW/m2 and maximum current density of 32.2 ± 0.3 A/m2 were obtained in the MFC after the acclimation by 1.0 V, respectively, which were 10.5 and 1610 times that of the unacclimated MFC. The MFC acclimated by 2.0 V could remain in stable operation with an average maximum current density of 7.8 ± 0.1 A/m2 and a maximum power density of 1439 ± 30 mW/m2 within 40 cycles (∼20 d). The average biomass of the anodic biofilms increased from 3.8 ± 0.9 mg/g before the acclimation to 11.3 ± 1.6 mg/g after the acclimation by 2.0 V. Correspondingly, the anode bacterial viability increased from 0.74 ± 0.02 to 0.91 ± 0.02. The relative abundance of Geoalkalibacter decreased from 18.7 % to 36.1 % before the acclimation to 1.3 %–18.0 % after the acclimation by 2.0 V in the bacterial communities of the anodic biofilms in the MFC. Results from this study should provide an easy way to enhance electrochemically active bacteria acclimation and improve electricity generation in the MFC.

Ofloxacin weakened treatment performance of rural domestic sewage in an aerobic biofilm system by affecting biofilm resistance, bacterial community, and functional genes

Ofloxacin (OFL) is a typical fluoroquinolone antibiotic widely detected in rural domestic sewage, however, its effects on the performance of aerobic biofilm systems during sewage treatment process remain poorly understood. We carried out an aerobic biofilm experiment to explore how the OFL with different concentrations affects the pollutant removal efficiency of rural domestic sewage. Results demonstrated that the OFL negatively affected pollutant removal in aerobic biofilm systems. High OFL levels resulted in a decrease in removal efficiency: 9.33% for chemical oxygen demand (COD), 18.57% for ammonium (NH4+-N), and 8.49% for total phosphorus (TP) after 35 days. The findings related to the chemical and biological properties of the biofilm revealed that the OFL exposure triggered oxidative stress and SOS responses, decreased the live cell number and extracellular polymeric substance content of biofilm, and altered bacterial community composition. More specifically, the relative abundance of key genera linked to COD (e.g., Rhodobacter), NH4+-N (e.g., Nitrosomonas), and TP (e.g., Dechlorimonas) removal was decreased. Such the OFL-induced decrease of these genera might result in the down-regulation of carbon degradation (amyA), ammonia oxidation (hao), and phosphorus adsorption (ppx) functional genes. The conventional pollutants (COD, NH4+-N, and TP) removal was directly affected by biofilm resistance, functional genes, and bacterial community under OFL exposure, and the bacterial community played a more dominant role based on partial least-squares path model analysis. These findings will provide valuable insights into understanding how antibiotics impact the performance of aerobic biofilm systems during rural domestic sewage treatment.

Interactions between water quality and microbes in epiphytic biofilm and superficial sediment of lake in trophic agriculture area

Epiphytic and superficial sediment biofilm-dwelling microbial communities play a pivotal role in water quality regulation and biogeochemical cycling in shallow lakes. However, the interactions are far from clear between water physicochemical parameters and microbial community on aquatic plants and in surface sediments of lake in trophic agriculture area. This study employed Illumina sequencing, Partial Least Squares Path Modeling (PLS-PM), and physico-chemical analytical methods to explore the interactions between water quality and microbes (bacteria and eukaryotes) in three substrates of trophic shallow Lake Cyohoha North, Rwanda. The Lake Cyohoha was significantly polluted with total phosphorus (TP), total nitrogen (TN), nitrate nitrogen (NO3-N), and ammonia nitrogen (NH3−N) in the wet season compared to the dry season. PLS-PM revealed a strong positive correlation (+0.9301) between land use types and physico-chemical variables in the rainy season. In three substrates of the trophic lake, Proteobacteria, Cyanobacteria, Firmicutes, and Actinobacteria were dominant phyla in the bacterial communities, and Rotifers, Platyhelminthes, Gastrotricha, and Ascomycota dominated in microeukaryotic communities. As revealed by null and neutral models, stochastic processes predominantly governed the assembly of bacterial and microeukaryotic communities in biofilms and surface sediments. Network analysis revealed that the microbial interconnections in Ceratophyllum demersum were more stable and complex compared to those in Eichhornia crassipes and sediments. Co-occurrence network analysis (|r| > 0.7, p < 0.05) revealed that there were complex interactions among physicochemical parameters and microbes in epiphytic and sediment biofilms, and many keystone microbes on three substrates played important role in nutrients removal, food web and microbial community stable. These findings emphasize that eutrophic water influence the structure, composition, and interactions of microbes in epiphytic and surface sediment biofilms, and provided new insights into the interconnections between water quality and microbial community in presentative substrates in tropical lacustrine ecosystems in agriculturally polluted areas. The study provides useful information for water quality protection and aquatic plants restoration for policy making and catchment management.

Characterization of biofilm bacterial communities in rural drainage system ancillary facilities

To investigate the differences in the bacterial communities of biofilms in the appurtenant facilities of rural sewage collection systems, a pilot research setup was constructed. A study was conducted using real sewage collected in a rural area, and the bacterial communities of biofilms in different appurtenant facilities were characterized using Illumina HiSeq high-throughput sequencing technology. The results showed that there were significant differences in biofilm bacterial communities among the different annexes. The biofilms from all four ancillary facilities (drop manhole, turning inspection well, mud trap, and direct inspection well) contained some amounts of denitrifying bacteria (relative abundance >6 %), but lacked ammonia- and nitrite-oxidizing bacteria (relative abundance <0.1 %). The relative abundance of sulfate-reducing bacteria was high (6.32 %), with Desulfobulbus being dominant (4.12 %) owing to the prolonged low dissolved oxygen environment in the sedimentation wells, which are at high risk of accumulating H2S relative to other ancillary facilities. All four ancillary facilities had high abundances of potential disease-causing bacteria (e.g., Acinetobacter and Arcobacter) in the biofilm and in the overwater. Therefore, the biosafety of the effluent should be taken into account in the collection process.

Microbial dynamics in Manaus river, Brazil

Rivers, which are vital ecosystems that support a variety of life forms and provide many ecosystem services, have been degraded by human activities, such as urbanization, pollution, and overexploitation. Habitat restoration projects have been implemented in different parts of the world to restore the ecological health and functioning of degraded rivers. The microbial community that forms biofilms on various substrates is one of the key components of river ecosystems. Organic matter is decomposed and carbon dioxide is produced by these biofilms, which affects the oxygen levels and nutrient cycles in the water. However, the effects of habitat restoration on the biofilm microbial community are not well understood. High-throughput DNA sequencing was used in this study to compare the bacterial composition of biofilms in three types of rivers: degraded urban rivers, urban rivers with restored habitats, and forested rivers that serve as reference conditions. The following questions were aimed to be answered: (i) How is the biofilm bacterial community composition affected by habitat restoration? (ii) How does bacterial diversity change in restored rivers compared to degraded and reference rivers? (iii) What are the environmental factors that influence the biofilm bacterial community composition? It was found that water quality was improved by habitat restoration by increasing the dissolved oxygen and reducing the organic pollutants in urban rivers. A decrease in bacterial diversity and a shift in the biofilm bacterial community structure towards that of the reference forested rivers were accompanied by this. This suggests that the biofilm microbial community can be altered by habitat restoration and its role in processing organic pollutants can be enhanced. However, it was also found that there was still a significant difference in the biofilm bacterial community between the restored and reference rivers, indicating that more time and effort are needed to achieve a similar ecological quality as the natural forested rivers.

Metabolic interactions affect the biomass of synthetic bacterial biofilm communities.

Co-occurrence network analysis is an effective tool for predicting complex networks of microbial interactions in the natural environment. Using isolates from a rhizosphere, we constructed multi-species biofilm communities and investigated co-occurrence patterns between microbial species in genome-scale metabolic models and in vitro experiments. According to our results, metabolic exchanges and resource competition may partially explain the co-occurrence network analysis results found in synthetic bacterial biofilm communities.

Effect of booster disinfection on the prevalence of microbial antibiotic resistance and bacterial community in a simulated drinking water distribution system

Booster disinfection was often applied to control the microorganism's growth in long-distance water supply systems. The effect of booster disinfection on the changing patterns of antibiotic resistance and bacterial community was investigated by a simulated water distribution system (SWDS). The results showed that the antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) were initially removed after dosing disinfectants (chlorine and chloramine), but then increased with the increasing water age. However, the relative abundance of ARGs significantly increased after booster disinfection both in buck water and biofilm, then decreased along the pipeline. The pipe materials and disinfectant type also affected the antibiotic resistance. Chlorine was more efficient in controlling microbes and ARGs than chloramine. Compared with UPVC and PE pipes, SS pipes had the lowest total bacteria, ARB concentration, and ARB percentage, mainly due to higher disinfectant residuals and a smoother surface. The significant correlation (rs = 0.77, p < 0.001) of the 16S rRNA genes was observed between buck water and biofilm, while the correlations of targeted ARGs were found to be weak. Bray-Curtis similarity index indicated that booster disinfection significantly changed the biofilm bacterial community and the disinfectant type also had a marked impact on the bacterial community. At the genus level, the relative abundance of Pseudomonas, Sphingomonas, and Methylobacterium significantly increased after booster disinfection. Mycobacterium increased after chloramination while decreased after chlorination, indicating Mycobacterium might resist chloramine. Pseudomonas, Methylobacterium, and Phreatobacter were found to correlate well with the relative abundance of ARGs. These results highlighted antibiotic resistance shift and bacterial community alteration after booster disinfection, which may be helpful in controlling potential microbial risk in drinking water.

Effects of Chlorella pyrenoidosa Supplementation on Water Quality, Shrimp Growth Performance, and Biofilm Bacterial Community Structure in Litopenaeus vannamei Aquaculture Systems

Chlorella pyrenoidosa is a widely used microalgae in the aquaculture process of Litopenaeus vannamei. In order to evaluate the effects of supplementing C. pyrenoidosa on water quality, shrimp growth performance, and biofilm bacterial community structure in L. vannamei aquaculture systems, C. pyrenoidosa suspension was supplemented in the precultured biofilm (PB) and water exchange (WE) culture systems. The results showed that supplementation with C. pyrenoidosa significantly increased the turbidity and the concentrations of total ammonia nitrogen (TAN) and nitrite nitrogen ( NO 2 − ─N) in the PBC system (the PB system supplemented with C. pyrenoidosa), but had no significant effect on those in the WEC system (the WE system supplemented with C. pyrenoidosa). However, the TAN concentration of all systems remained at a low level (&lt;0.1 mg/L) throughout the experiment. Additionally, supplementation with C. pyrenoidosa decreased the final concentrations of total phosphorus in the PBC and WEC systems by 15.74% and 23.33%, respectively. With the supplementation of C. pyrenoidosa, the final weight, final biomass, and average daily growth rate of L. vannamei increased, while the feed conversion ratio decreased. 16srRNA high-throughput sequencing results showed that the supplementation of C. pyrenoidosa to the PBC system resulted in a decrease in the relative abundances of Proteobacteria and Bacteroidetes and an increase in the relative abundance of Acidobacteria. Compared to those in the initial biofilm sample, the relative abundances of nitrifying bacteria, Nitrosococcus, Nitrosomonas, Nitrococcus, and Nitrospira, in PBCF (biofilm in the PB systems with C. pyrenoidosa) and PBOF (biofilm in the PB systems without C. pyrenoidosa) decreased from 10.18% to 3.05% and 0.75%, respectively. In conclusion, C. pyrenoidosa, as a supplement to the aquaculture systems, has practical application prospects.