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The effect of norepinephrine as a compound modulating the activity of the antibiotic azithromycin on single-species and binary biofilms of members of the human microbiota, Staphylococcus aureus and Kytococcus schroeteri, was studied in various model systems. At the concentration of 3.55 µM, the hormone was shown to be able, depending on the cultivation system and incubation time, of both enhancing and weakening the effects of azithromycin at subinhibitory concentrations (0.001 and 4 µg/mL). In the case of rapidly formed biofilms, norepinephrine weakened the inhibitory effect of the antibiotic, while in the presence of the full stage of adhesion the hormone, on the contrary, enhanced the inhibitory effect. Interaction between two microorganisms in the community was no less important, since the presence of K. schroeteri in the community changed the effect of azithromycin (4 μg/mL) in combination with norepinephrine on S. aureus. It was shown that azithromycin and norepinephrine, as well as their combinations, were able to change the expression of the genes coding resistance not only to macrolides (increased expression of the mrx gene by a combination of 4 μg/mL azithromycin and 3.55 μM norepinephrine), but also to fluoroquinolones (decreased expression of the arlR gene and increased one of mdtK). [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study is to investigate the antimicrobial efficacy of antimicrobial photodynamic therapy (PDT) using natural photosensitizers (curcumin, riboflavin, and phycocyanin) and light-emitting diode (LED) irradiation against multispecies biofilms in an acrylic denture base model. Materials and Methods: Forty-five acrylic specimens were fabricated using heat-curing acrylic resin. The specimens were then infected with a mixed culture of bacterial and fungal species (including Streptococcus mutans, Streptococcus sanguinis, Candida albicans, and Candida glabrata) for 4 days. The acrylic discs were divided into nine groups, with each group containing five discs: control, 0.2% chlorhexidine, 5.25% sodium hypochlorite, curcumin, riboflavin, phycocyanin alone or along with LED. After treatment, the number of colony-forming units (CFUs) per milliliter was counted. In addition, the extent of biofilm degradation was assessed using the crystal violet staining method and scanning electron microscopy. Results: All experimental groups exhibited a significant reduction in colony numbers for both bacterial and fungal species compared to the control (p < 0.001). The PDT groups exhibited a statistically significant reduction in colony counts for both bacteria and fungi compared to the photosensitizer-only groups. Conclusions: The results of this in vitro study show that PDT with natural photosensitizers and LED devices can effectively reduce the viability and eradicate the biofilm of microorganisms responsible for causing denture infections. [ABSTRACT FROM AUTHOR]

Disinfectants are used as the main agents against microorganisms circulating on the surfaces of food enterprises. However, the adaptive ability of microorganisms to form biofilms complicates the process of surface cleaning and reduces the effectiveness of disinfectants. Modern disinfectants act against freely circulating microflora, but it is known that they are not always effective against biofilms. The purpose of this study was to investigate effective disinfectant compositions with bactericidal effect on binary bacterial biofilms of different ages. The article describes the effects of disinfectants based on chlorine, peracetic acid and quaternary ammonium compounds with enzymes in concentrations recommended by the manufacturer and increased several times on Salmonella 38, Brochothrix thermosphacta 2726 and Staphylococcus equorum 2736 planktonic cultures and binary biofilms. Binary biofilms of different ages (2 and 9 days old) were exposed to disinfectants with various active ingredients in combination with adjuvants, i. e. hydrogen peroxide 6% and various concentrations of isopropyl alcohol (30%). All products in concentrations recommended by the manufacturer did not have a disinfectant effect against the studied biofilm cultures. As a result of the work, it was found that the most effective disinfectants against multispecies biofilms were quaternary ammonium compounds in combination with enzymes and chlorine in combination with isopropyl alcohol (30%). The results obtained allow to expand knowledge about effective methods for controlling biofilms.

Salmonella enterica is a leading cause of foodborne illness in the U.S. In the meat industry, one action taken to address pathogen contamination incidence is an intense sanitization (IS) of the entire processing plant that many large processors perform annually or semiannually. However, this procedure’s immediate and long-term impact on environment microbial community and pathogen colonization are unknown. Here we investigated the impact of IS procedure on environmental biofilms and the subsequent S. enterica colonization and stress tolerance. Environmental samples were collected from floor drains at various areas 1  week before, 1  week, and 4  weeks after the IS procedure at a beef plant with sporadic S. enterica prevalence. Biofilm formation by microorganisms in the drain samples without S. enterica presence was tested under processing temperature. The ability of the biofilms to recruit and/or protect a co-inoculated S. enterica strain from quaternary ammonium compound (QAC) treatment was determined. The community structure of each drain sample was elucidated through 16S rRNA amplicon community sequencing. Post-IS samples collected from 8 drains formed significantly stronger biofilms than the respective pre-IS samples. S. enterica colonization was not different between the pre- and postIS biofilms at all drain locations. S. enterica survival in QAC-treated pre- and post-IS mixed biofilms varied depending upon the drain location but a higher survival was associated with a stronger biofilm matrix. The 16S rRNA amplicon gene community sequencing results exhibited a decrease in community diversity 1  week after IS treatment but followed by a significant increase 4  weeks after the treatment. The IS procedure also significantly altered the community composition and the higher presence of certain species in the postIS community may be associated with the stronger mixed biofilm formation and Salmonella tolerance. Our study suggested that the IS procedure might disrupt the existing environmental microbial community and alter the natural population composition, which might lead to unintended consequences as a result of a lack of competition within the multispecies mixture. The survival and recruitment of species with high colonizing capability to the post-IS community may play crucial roles in shaping the ensuing ecological dynamics. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study is to investigate the antimicrobial efficacy of antimicrobial photodynamic therapy (PDT) using natural photosensitizers (curcumin, riboflavin, and phycocyanin) and light-emitting diode (LED) irradiation against multispecies biofilms in an acrylic denture base model. Materials and Methods: Forty-five acrylic specimens were fabricated using heat-curing acrylic resin. The specimens were then infected with a mixed culture of bacterial and fungal species (including Streptococcus mutans, Streptococcus sanguinis, Candida albicans, and Candida glabrata) for 4 days. The acrylic discs were divided into nine groups, with each group containing five discs: control, 0.2% chlorhexidine, 5.25% sodium hypochlorite, curcumin, riboflavin, phycocyanin alone or along with LED. After treatment, the number of colony-forming units (CFUs) per milliliter was counted. In addition, the extent of biofilm degradation was assessed using the crystal violet staining method and scanning electron microscopy. Results: All experimental groups exhibited a significant reduction in colony numbers for both bacterial and fungal species compared to the control (p < 0.001). The PDT groups exhibited a statistically significant reduction in colony counts for both bacteria and fungi compared to the photosensitizer-only groups. Conclusions: The results of this in vitro study show that PDT with natural photosensitizers and LED devices can effectively reduce the viability and eradicate the biofilm of microorganisms responsible for causing denture infections.

It has been established that the human atrial natriuretic peptide is able to alter the effect of azithromycin on Kytococcus schroeteri H01 and Staphylococcus aureus 209P monospecies and binary biofilms. The effect of the hormone depends on the surface type and cultivation system, and it may have both enhancing and counteracting effects. The antagonistic effect of the hormone was observed mostly on hydrophobic surfaces, whereas the additive effect was observed on hydrophilic surfaces like glass. Also, the effect of the hormone depends on the antibiotic concentration and bacterial species. The combination of azithromycin and ANP led to an amplification of cell aggregation in biofilms, to the potential increase in matrix synthesis, and to a decrease in S. aureus in the binary community. Also, ANP, azithromycin, and their combinations caused the differential expression of genes of resistance to different antibiotics, like macrolides (mostly increasing expression in kytococci), fluoroquinolones, aminoglycosides, and others, in both bacteria. [ABSTRACT FROM AUTHOR]

Iron acquisition is of fundamental importance for microorganisms, since this metal is generally poorly bioavailable under natural conditions. Fe is mostly present as a ferric form in soils, which strongly limits its bioavailability, while most soil bacteria are tightly packed within multicellular communities named biofilms. This research showed that biofilm formation by a gram-positive bacterium Bacillus subtilis during the interactions with other microbial species was both essential to ensure Fe uptake from the environment and to maintain the cellular Fe homeostasis. The biofilm matrix appeared to play an important role, favoring the efficient usage of siderophores. Taken together, these results demonstrate a close link between biofilm formation and iron acquisition in B. subtilis and Escherichia coli, allowing a better comprehension of how bacteria can cope with metal limitation under environmental conditions. [ABSTRACT FROM AUTHOR]

A series of biocide-containing polyethylene composites were obtained using novel guanidine-containing copolymers immobilized on an inert mineral carrier. Multispecies microbial communities were isolated from the surface of polyethylene samples either incubated or found in the environment, and their taxonomic composition was determined. Biofilms reconstructed using microorganisms obtained from different ecotopes were shown to intensively foul polyethylene surfaces. The presence of polyguanidine biocide suppressed the growth and survival of both binary and multispecies biofilms, with a cumulative effect during long-term incubation. When microorganisms were co-cultivated in binary biofilms, the phenomenon of a decrease in biocide effectiveness was demonstrated. This protective effect is potentially based on cooperative interactions inside the binary biofilm community. Scanning electron microscopy showed a pronounced difference in the architecture of reconstructed biofilms incubated in the presence of biocide in comparison to control samples, where biocide suppressed the formation of dense and well-organized three-dimensional structures. Biofilm disruption by immobilized biocides occurred primarily during the later stages of biofilm formation, probably caused by polycation interaction with their negatively charged extracellular components. [ABSTRACT FROM AUTHOR]

In this study, we evaluated effects of the osmolality of the cultivating on the biofilm development and architecture of biofilms of the bacterium (B. subtilis) during their interactions with Escherichia coli K-12 1655 strains. At cultivation in the cultural medium without NaCl, the bacterial growth rates of single-species biofilms of Bacillus subtilis strains and biofilms as result of their interaction with Escherichia coli strains were similar and determines the mutualism between two strains in the structure of biofilms, but the concentration of NaCl in the cultural medium over of 100 mM lead to the impeded growth and affect adversely the process of biofilm formation by the participation ofB.subtilis 170 and E.coli K-12 1655, B.subtilis 168 and E.coli K-12 1655 strains, and inhibits spore formation. [ABSTRACT FROM AUTHOR]

Early childhood caries (ECC) is a public healthcare concern that greatly reduces the quality of life of young children. As a leading factor of ECC, cariogenic biofilms are composed of acidogenic/aciduric pathogens and extracellular polysaccharides (EPSs), creating an acidic and protected microenvironment. Antimicrobial photodynamic therapy (aPDT) is a noninvasive, painless, and efficient therapeutic approach that is suitable for treating ECC. However, due to the hyperfine structure of cariogenic biofilms, most photosensitizers (PSs) could not access and penetrate deeply in biofilms, which dramatically hamper their efficiency in the clinic. Herein, bioresponsive nanoparticle loaded with chlorin e6 (MPP-Ce6) is developed, which largely increases the penetration depth (by over 75%) and retention (by over 100%) of PS in the biofilm compared with free Ce6. Furthermore, MPP-Ce6-mediated aPDT not only kills the bacteria in preformed biofilms but also inhibits multispecies biofilm formation. A rampant caries model is established to mimic ECC in vivo, where the population of cariogenic bacteria is decreased to 10% after MPP-Ce6-mediated aPDT. Importantly, the number and severity of carious lesions are efficiently reduced via Keyes’ scoring and micro-CT analysis. This simple but effective strategy can serve as a promising approach for daily oral hygiene in preventing ECC.

Biofilms are complex structures with an intricate relationship between the resident microorganisms, the extracellular matrix, and the surrounding environment. Interest in biofilms is growing exponentially given its ubiquity in so diverse fields such as healthcare, environmental and industry. Molecular techniques (e.g., next-generation sequencing, RNA-seq) have been used to study biofilm properties. However, these techniques disrupt the spatial structure of biofilms; therefore, they do not allow to observe the location/position of biofilm components (e.g., cells, genes, metabolites), which is particularly relevant to explore and study the interactions and functions of microorganisms. Fluorescence in situ hybridization (FISH) has been arguably the most widely used method for an in situ analysis of spatial distribution of biofilms. In this review, an overview on different FISH variants already applied on biofilm studies (e.g., CLASI-FISH, BONCAT-FISH, HiPR-FISH, seq-FISH) will be explored. In combination with confocal laser scanning microscopy, these variants emerged as a powerful approach to visualize, quantify and locate microorganisms, genes, and metabolites inside biofilms. Finally, we discuss new possible research directions for the development of robust and accurate FISH-based approaches that will allow to dig deeper into the biofilm structure and function.

Simple Summary: Commensal ('friendly') microbes protect our skin from the invasion of pathogens and provide benefits for the human immune system. The microbial community exists in different microniches of the skin in the form of a biofilm—a highly organized microbial community, with properties different from traditionally studied planktonic cultures. The two most abundant skin commensals, Staphylococcus epidermidis and Cutibacterium acnes, can form biofilms inside hair follicles and sebaceous glands, and the behavior of these bacteria can maintain skin health. The study of the potential regulation of the skin microbial community (skin microbiota) by human hormones and particularly by human natriuretic peptides (NUP) has wide perspectives because of a data shortage, hormone potential to regulate the microbial community, and potential approaches in clinical practice. We used different methods to evaluate the impact of C-type natriuretic peptide (CNP) on monospecies and dual species biofilms of C. acnes and S. epidermidis, and we found that CNP boosts the competitive properties of C. acnes in the presence of S. epidermidis. Additionally, we found genes which are potential targets of CNP, hence, we made a step towards a better understanding of how peptides regulate the behavior of cutaneous bacteria populations. The effect of C-type natriuretic peptide in a concentration closer to the normal level in human blood plasma was studied on the mono-species and dual-species biofilms of the skin commensal bacteria Cutibacterium acnes HL043PA2 and Staphylococcus epidermidis ATCC14990. Despite the marginal effect of the hormone on cutibacteria in mono-species biofilms, the presence of staphylococci in the community resulted in a global shift of the CNP effect, which appeared to increase the competitive properties of C. acnes, its proliferation and the metabolic activity of the community. S. epidermidis was mostly inhibited in the presence of CNP. Both bacteria had a significant impact on the gene expression levels revealed by RNA-seq. CNP did not affect the gene expression levels in mono-species cutibacterial biofilms; however, in the presence of staphylococci, five genes were differentially expressed in the presence of the hormone, including two ribosomal proteins and metal ABC transporter permease. In staphylococci, the Na-translocating system protein MpsB NADH-quinone oxidoreductase subunit L was downregulated in the dual-species biofilms in the presence of CNP, while in mono-species biofilms, two proteins of unknown function were downregulated. Hypothetically, at least one of the CNP mechanisms of action is via the competition for zinc, at least on cutibacteria. [ABSTRACT FROM AUTHOR]

Biosurfactants of microbial origin are characterised by anti-adhesive properties and cause destruction of the overall structure of biofilms, which are distinguished by their amphiphilic nature. The anti-adhesion properties of biosurfactants are determined by the characteristics of the surface layer on which the microbial cell is attached, the temperature and the composition of the nutrient medium. The present study describes the role of antifungal compound from Bacillus spp. strain on the formation of mixed biofilms in the process of their co-cultivation of Bacillus subtilis and Escherichia coli strains. The study demonstrated the biofilm inhibition and dislodging activity of heat stable lipopeptides biosurfactant isolated from B. subtilis 170 strain. The crude biosurfactant, produced by B. subtilis 170 strain, exhibited antibiofilm activity against co-cultures of B. subtilis 170 and E. coli K-12 1655, B. subtilis 168 and E. coli K-12 1655 strains, a.m. the used biosurfactant at sub-inhibitory concentrations was effective as an anti-adhesive and biofilm disrupting agent against the studied isolate. In conclusion, this study reveals for the first time the potent activity of microbial biosurfactants against multispecies preformed biofilms, thus providing new directions toward the use and their development for application in industrial, ecological and biomedical practice. [ABSTRACT FROM AUTHOR]

It has been established that the human atrial natriuretic peptide is able to alter the effect of azithromycin on Kytococcus schroeteri H01 and Staphylococcus aureus 209P monospecies and binary biofilms. The effect of the hormone depends on the surface type and cultivation system, and it may have both enhancing and counteracting effects. The antagonistic effect of the hormone was observed mostly on hydrophobic surfaces, whereas the additive effect was observed on hydrophilic surfaces like glass. Also, the effect of the hormone depends on the antibiotic concentration and bacterial species. The combination of azithromycin and ANP led to an amplification of cell aggregation in biofilms, to the potential increase in matrix synthesis, and to a decrease in S. aureus in the binary community. Also, ANP, azithromycin, and their combinations caused the differential expression of genes of resistance to different antibiotics, like macrolides (mostly increasing expression in kytococci), fluoroquinolones, aminoglycosides, and others, in both bacteria.

In a large part of ecological niches, bacterial species are united in communities and develop together in the form of heterogeneous structures called biofilms, which are formed on surfaces of different nature s In this study, we evaluated effects of the D-alanine in the cultural medium on the biofilm development and architecture of biofilms of the bacterium (B. subtilis) as well as their interactions with Escherichia coli K-12 1655 strain. Effects of the D-alanine in the cultural medium on bacterial biofilm formation and the mechanisms were analyzed by the crystal violet staining method combined with cultivated microbial analysis, and confocal laser scanning microscopy. A 24 h mature Bacillus subtilis and Escherichia coli dual-species biofilms were exposed to different concentrations of D-alanine in the cultural medium. A series of experiments on the cultivation of biofilms in M63 medium (0.02 M KH2PO4, 0.04 M K2HPO4, 0.02 M (NH4)2SO4, 0.1 mM MgSO4 and 0.04 M glucose) were carried out according to the indicated scheme at D-alanine of 5, 6 and 8.5 mM. Тhe concentration of D-alanine in the cultural medium over of 5 mM lead to the impeded growth and affect adversely the process of biofilm formation by the participation of B. subtilis 170 and E. coli K-12 1655, B. subtilis 168 and E. coli K-12 1655 strains. [ABSTRACT FROM AUTHOR]

Bifidobacterium bifidum is part of the core microbiota of healthy infant guts where it may form biofilms on epithelial cells, mucosa, and food particles in the gut lumen. Little is known about transcriptional changes in B. bifidum engaged in synergistic multispecies biofilms with ecologically relevant species of the human gut. Recently, we reported prevalence of synergism in mixed-species biofilms formed by the human gut microbiota. This study represents a comparative gene expression analysis of B. bifidum when grown in a single-species biofilm and in two multispecies biofilm consortia with Bifidobacterium longum subsp. infantis, Bacteroides ovatus, and Parabacteroides distasonis in order to identify genes involved in this adaptive process in mixed biofilms and the influence on its metabolic and functional traits. Changes up to 58% and 43% in its genome were found when it grew in three- and four-species biofilm consortia, respectively. Upregulation of genes of B. bifidum involved in carbohydrate metabolism (particularly the galE gene), quorum sensing (luxS and pfs), and amino acid metabolism (especially branched chain amino acids) in both multispecies biofilms, compared to single-species biofilms, suggest that they may be contributing factors for the observed synergistic biofilm production when B. bifidum coexists with other species in a biofilm. [ABSTRACT FROM AUTHOR]

In various natural ecosystems, bacteria most often live in a sessile state enchased in a self-produced extracellular matrix forming biofilms. Due to their either negative or positive impact on different aspects of our daily life, the number of studies devoted to biofilms is increasing. Most research is based on biofilms formed by a single bacterial species. These simple models allowed the understanding of the mechanisms involved in biofilms formation and regulation. This likewise helped the development of several means to control the biofilms formation. However, these models do not closely mimic the natural biofilms known as biochemically and microbiologically heterogeneous and dynamic structures. For this reason, current studies focus more on multispecies biofilms using complex models to best approximate the natural environment. In this review, we addressed on available examples of multispecies biofilms in different domains to illustrate the complexity and organization of life within a consortium. Finally, we review the most used analytical techniques to study multispecies biofilms highlighting the need of multi-scale strategies to better decipher this complex lifestyle. • Natural biofilms are biochemically and microbiologically heterogeneous and dynamic structures • Complex biofilms are consortia subjected to complex interactions impacting their spatial organization and biomass production • Studying the multispecies biofilms requires a combined multidisciplinary technique • Biofilm modeling is required to get as close as possible to real natural conditions [ABSTRACT FROM AUTHOR]

Acne vulgaris is a common chronic inflammatory skin disease involving Cutibacterium acnes with other skin commensals such as Staphylococcus aureus and Candida albicans in the anaerobic and lipid-rich conditions of pilosebaceous units. These microbes readily form multispecies biofilms that are tolerant of traditional antibiotics as well as host immune systems. The phytopigment alizarin was previously found to prevent biofilm formation by S. aureus and C. albicans strains under aerobic conditions. Hence, we hypothesized that alizarin might control C. acnes and multispecies biofilm development. We found that under anaerobic conditions, alizarin efficiently inhibited single biofilm formation and multispecies biofilm development by C. acnes, S. aureus, and C. albicans without inhibiting planktonic cell growth. Alizarin increased the hydrophilicities of S. aureus and C. albicans cells, decreased lipase production by S. aureus, diminished agglutination by C. acnes, and inhibited the aggregation of C. albicans cells. Furthermore, the co-administration of alizarin and antibiotics enhanced the antibiofilm efficacies of alizarin against C. acnes. A transcriptomic study showed that alizarin repressed the transcriptions of various biofilm-related genes such as lipase, hyaluronate lyase, adhesin/invasion-related, and virulence-related genes of C. acnes. Furthermore, alizarin at 100 µg/mL prevented C. acnes biofilm development on porcine skin. Our results show that alizarin inhibits multispecies biofilm development by acne-causing microbes and suggest it might be a useful agent for treating or preventing C. acnes-causing skin diseases. [ABSTRACT FROM AUTHOR]

Dental caries, an ecological dysbiosis of oral microflora, initiates from the virulent biofilms formed on tooth surfaces where cariogenic microorganisms metabolize dietary carbohydrates, producing acid that demineralizes tooth enamel. Forming cariogenic biofilms, Streptococcus mutans and Candida albicans are well-recognized and emerging pathogens for dental caries. Recently, probiotics have demonstrated their potential in treating biofilm-related diseases, including caries. However, limited studies have assessed their effect on cariogenic bacteria–fungi cross-kingdom biofilm formation and their underlying interactions. Here, we assessed the effect of four probiotic Lactobacillus strains (Lactobacillus rhamnosus ATCC 2836, Lactobacillus plantarum ATCC 8014, Lactobacillus plantarum ATCC 14917, and Lactobacillus salivarius ATCC 11741) on S. mutans and C. albicans using a comprehensive multispecies biofilm model that mimicked high caries risk clinical conditions. Among the tested probiotic species, L. plantarum demonstrated superior inhibition on the growth of C. albicans and S. mutans , disruption of virulent biofilm formation with reduced bacteria and exopolysaccharide (EPS) components, and formation of virulent microcolonies structures. Transcriptome analysis (RNA sequencing) further revealed disruption of S. mutans and C. albicans cross-kingdom interactions with added L. plantarum. Genes of S. mutans and C. albicans involved in metabolic pathways (e.g., EPS formation, carbohydrate metabolism, glycan biosynthesis, and metabolism) were significantly downregulated. More significantly, genes related to C. albicans resistance to antifungal medication (ERG4), fungal cell wall chitin remodeling (CHT2), and resistance to oxidative stress (CAT1) were also significantly downregulated. In contrast, Lactobacillus genes plnD , plnG , and plnN that contribute to antimicrobial peptide plantaricin production were significantly upregulated. Our novel study findings support further assessment of the potential role of probiotic L. plantarum for cariogenic biofilm control. [ABSTRACT FROM AUTHOR]

Periodontal disease depends on the presence of different microorganisms in the oral cavity that during the colonization of periodontal tissues form a multispecies biofilm community, thus allowing them to survive under adverse conditions or facilitate further colonization of host tissues. Not only numerous bacterial species participate in the development of biofilm complex structure but also fungi, especially Candida albicans , that often commensally inhabits the oral cavity. C. albicans employs an extensive armory of various virulence factors supporting its coexistence with bacteria resulting in successful host colonization and propagation of infection. In this article, we highlight various aspects of individual fungal virulence factors that may facilitate the collaboration with the associated bacterial representatives of the early colonizers of the oral cavity, the bridging species, and the late colonizers directly involved in the development of periodontitis, including the "red complex" species. In particular, we discuss the involvement of candidal cell surface proteins—typical fungal adhesins as well as originally cytosolic "moonlighting" proteins that perform a new function on the cell surface and are also present within the biofilm structures. Another group of virulence factors considered includes secreted aspartic proteases (Sap) and other secreted hydrolytic enzymes. The specific structure of the candidal cell wall, dynamically changing during morphological transitions of the fungus that favor the biofilm formation, is equally important and discussed. The non-protein biofilm-composing factors also show dynamic variability upon the contact with bacteria, and their biosynthesis processes could be involved in the stability of mixed biofilms. Biofilm-associated changes in the microbe communication system using different quorum sensing molecules of both fungal and bacterial cells are also emphasized in this review. All discussed virulence factors involved in the formation of mixed biofilm pose new challenges and influence the successful design of new diagnostic methods and the application of appropriate therapies in periodontal diseases. [ABSTRACT FROM AUTHOR]

Dental caries, an ecological dysbiosis of oral microflora, initiates from the virulent biofilms formed on tooth surfaces where cariogenic microorganisms metabolize dietary carbohydrates, producing acid that demineralizes tooth enamel. Forming cariogenic biofilms, Streptococcus mutans and Candida albicans are well-recognized and emerging pathogens for dental caries. Recently, probiotics have demonstrated their potential in treating biofilm-related diseases, including caries. However, limited studies have assessed their effect on cariogenic bacteria–fungi cross-kingdom biofilm formation and their underlying interactions. Here, we assessed the effect of four probiotic Lactobacillus strains (Lactobacillus rhamnosus ATCC 2836, Lactobacillus plantarum ATCC 8014, Lactobacillus plantarum ATCC 14917, and Lactobacillus salivarius ATCC 11741) on S. mutans and C. albicans using a comprehensive multispecies biofilm model that mimicked high caries risk clinical conditions. Among the tested probiotic species, L. plantarum demonstrated superior inhibition on the growth of C. albicans and S. mutans, disruption of virulent biofilm formation with reduced bacteria and exopolysaccharide (EPS) components, and formation of virulent microcolonies structures. Transcriptome analysis (RNA sequencing) further revealed disruption of S. mutans and C. albicans cross-kingdom interactions with added L. plantarum. Genes of S. mutans and C. albicans involved in metabolic pathways (e.g., EPS formation, carbohydrate metabolism, glycan biosynthesis, and metabolism) were significantly downregulated. More significantly, genes related to C. albicans resistance to antifungal medication (ERG4), fungal cell wall chitin remodeling (CHT2), and resistance to oxidative stress (CAT1) were also significantly downregulated. In contrast, Lactobacillus genes plnD, plnG, and plnN that contribute to antimicrobial peptide plantaricin production were significantly upregulated. Our novel study findings support further assessment of the potential role of probiotic L. plantarum for cariogenic biofilm control.

ABSTRACT The Gram-positive anaerobic bacterium Cutibacterium acnes is a major inhabitant of human skin and has been implicated in acne vulgaris formation and in the formation of multispecies biofilms with other skin-inhabiting organisms like Staphylococcus aureus and Candida albicans. Indoles are widespread in nature (even in human skin) and function as important signaling molecules in diverse prokaryotes and eukaryotes. In the present study, we investigated the antibacterial and antibiofilm activities of 20 indoles against C. acnes. Of the indoles tested, indole-3-carbinol at 0.1 mM significantly inhibited biofilm formation by C. acnes without affecting planktonic cell growth, and the anticancer drug 3,3′-diindolylmethane (DIM) at 0.1 mM (32 μg/mL) also significantly inhibited planktonic cell growth and biofilm formation by C. acnes, whereas the other indoles and indole itself were less effective. Also, DIM at 0.1 mM successfully inhibited multispecies biofilm formation by C. acnes, S. aureus, and C. albicans. Transcriptional analyses showed that DIM inhibited the expressions of several biofilm-related genes in C. acnes, and at 0.05 mM, DIM inhibited hyphal formation and cell aggregation by C. albicans. These results suggest that DIM and other indoles inhibit biofilm formation by C. acnes and have potential use for treating C. acnes associated diseases. IMPORTANCE Since indoles are widespread in nature (even in human skin), we hypothesized that indole and its derivatives might control biofilm formation of acne-causing bacteria (Cutibacterium acnes and Staphylococcus aureus) and fungal Candida albicans. The present study reports for the first time the antibiofilm and antimicrobial activities of several indoles on C. acnes. Of the indoles tested, two anticancer agents, indole-3-carbinol and 3,3′-diindolylmethane found in cruciferous vegetables, significantly inhibited biofilm formation by C. acnes. Furthermore, the most active 3,3′-diindolylmethane successfully inhibited multispecies biofilm formation by C. acnes, S. aureus, and C. albicans. Transcriptional analyses showed that 3,3′-diindolylmethane inhibited the expressions of several biofilm-related genes including lipase, hyaluronate lyase, and virulence-related genes in C. acnes, and 3,3′-diindolylmethane inhibited hyphal formation and cell aggregation by C. albicans. Our findings show that 3,3′-diindolylmethane offers a potential means of controlling acne vulgaris and multispecies biofilm-associated infections due to its antibiofilm and antibiotic properties.

Periodontal disease depends on the presence of different microorganisms in the oral cavity that during the colonization of periodontal tissues form a multispecies biofilm community, thus allowing them to survive under adverse conditions or facilitate further colonization of host tissues. Not only numerous bacterial species participate in the development of biofilm complex structure but also fungi, especially Candida albicans, that often commensally inhabits the oral cavity. C. albicans employs an extensive armory of various virulence factors supporting its coexistence with bacteria resulting in successful host colonization and propagation of infection. In this article, we highlight various aspects of individual fungal virulence factors that may facilitate the collaboration with the associated bacterial representatives of the early colonizers of the oral cavity, the bridging species, and the late colonizers directly involved in the development of periodontitis, including the “red complex” species. In particular, we discuss the involvement of candidal cell surface proteins—typical fungal adhesins as well as originally cytosolic “moonlighting” proteins that perform a new function on the cell surface and are also present within the biofilm structures. Another group of virulence factors considered includes secreted aspartic proteases (Sap) and other secreted hydrolytic enzymes. The specific structure of the candidal cell wall, dynamically changing during morphological transitions of the fungus that favor the biofilm formation, is equally important and discussed. The non-protein biofilm-composing factors also show dynamic variability upon the contact with bacteria, and their biosynthesis processes could be involved in the stability of mixed biofilms. Biofilm-associated changes in the microbe communication system using different quorum sensing molecules of both fungal and bacterial cells are also emphasized in this review. All discussed virulence factors involved in the formation of mixed biofilm pose new challenges and influence the successful design of new diagnostic methods and the application of appropriate therapies in periodontal diseases.

The effect of C-type natriuretic peptide in a concentration closer to the normal level in human blood plasma was studied on the mono-species and dual-species biofilms of the skin commensal bacteria Cutibacterium acnes HL043PA2 and Staphylococcus epidermidis ATCC14990. Despite the marginal effect of the hormone on cutibacteria in mono-species biofilms, the presence of staphylococci in the community resulted in a global shift of the CNP effect, which appeared to increase the competitive properties of C. acnes, its proliferation and the metabolic activity of the community. S. epidermidis was mostly inhibited in the presence of CNP. Both bacteria had a significant impact on the gene expression levels revealed by RNA-seq. CNP did not affect the gene expression levels in mono-species cutibacterial biofilms; however, in the presence of staphylococci, five genes were differentially expressed in the presence of the hormone, including two ribosomal proteins and metal ABC transporter permease. In staphylococci, the Na-translocating system protein MpsB NADH-quinone oxidoreductase subunit L was downregulated in the dual-species biofilms in the presence of CNP, while in mono-species biofilms, two proteins of unknown function were downregulated. Hypothetically, at least one of the CNP mechanisms of action is via the competition for zinc, at least on cutibacteria.

In food processing environments, various microorganisms can adhere and aggregate on the surface of equipment, resulting in the formation of multispecies biofilms. Complex interactions among microorganisms may affect the formation of multispecies biofilms and resistance to disinfectants, which are food safety and quality concerns. This article reviews the various interactions among microorganisms in multispecies biofilms, including competitive, cooperative, and neutral interactions. Then, the preliminary mechanisms underlying the formation of multispecies biofilms are discussed in relation to factors, such as quorum-sensing signal molecules, extracellular polymeric substances, and biofilm-regulated genes. Finally, the resistance mechanisms of common contaminating microorganisms to disinfectants in food processing environments are also summarized. This review is expected to facilitate a better understanding of interspecies interactions and provide some implications for the control of multispecies biofilms in food processing. Multispecies interaction of biofilms is often cooperative, competitive, or neutral. QS molecules, EPS, and biofilm-regulated genes affect multispecies biofilm formation. Disinfectant resistance of multispecies biofilms depends on EPS and biofilm age. Studies of multispecies biofilms are less focused on high-diversity biofilms. [ABSTRACT FROM AUTHOR]

Acne vulgaris is a common chronic inflammatory skin disease involving Cutibacterium acnes with other skin commensals such as Staphylococcus aureus and Candida albicans in the anaerobic and lipid-rich conditions of pilosebaceous units. These microbes readily form multispecies biofilms that are tolerant of traditional antibiotics as well as host immune systems. The phytopigment alizarin was previously found to prevent biofilm formation by S. aureus and C. albicans strains under aerobic conditions. Hence, we hypothesized that alizarin might control C. acnes and multispecies biofilm development. We found that under anaerobic conditions, alizarin efficiently inhibited single biofilm formation and multispecies biofilm development by C. acnes, S. aureus, and C. albicans without inhibiting planktonic cell growth. Alizarin increased the hydrophilicities of S. aureus and C. albicans cells, decreased lipase production by S. aureus, diminished agglutination by C. acnes, and inhibited the aggregation of C. albicans cells. Furthermore, the co-administration of alizarin and antibiotics enhanced the antibiofilm efficacies of alizarin against C. acnes. A transcriptomic study showed that alizarin repressed the transcriptions of various biofilm-related genes such as lipase, hyaluronate lyase, adhesin/invasion-related, and virulence-related genes of C. acnes. Furthermore, alizarin at 100 µg/mL prevented C. acnes biofilm development on porcine skin. Our results show that alizarin inhibits multispecies biofilm development by acne-causing microbes and suggest it might be a useful agent for treating or preventing C. acnes-causing skin diseases.

The lungs of cystic fibrosis (CF) patients are often chronically colonized by multiple microbial species that can form biofilms, including the major CF pathogen Pseudomonas aeruginosa. Herewith, lower microbial diversity in CF airways is typically associated with worse health outcomes. In an attempt to treat CF lung infections patients are frequently exposed to antibiotics, which may affect microbial diversity. This study aimed at understanding if common antibiotics that target P. aeruginosa influence microbial diversity. To this end, a microaerophilic multispecies biofilm model of frequently co-isolated members of the CF lung microbiome (Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus anginosus, Achromobacter xylosoxidans, Rothia mucilaginosa, and Gemella haemolysans) was exposed to antipseudomonal antibiotics. We found that antibiotics that affected several dominant species (i.e. ceftazidime, tobramycin) resulted in higher species evenness compared to colistin, which is only active against P. aeruginosa. Furthermore, susceptibility of individual species in the multispecies biofilm following antibiotic treatment was compared to that of the respective single-species biofilms, showing no differences. Adding three anaerobic species (Prevotella melaninogenica, Veillonella parvula, and Fusobacterium nucleatum) to the multispecies biofilm did not influence antibiotic susceptibility. In conclusion, our study demonstrates antibiotic-dependent effects on microbial community diversity of multispecies biofilms comprised of CF microbiome members.

The mechanisms of microbial action on synthetic plastics are analyzed, with the focus on the most widespread polymers produced on an industrial scale. The effect of microbial enzymes on plastic biodegradation and the role of multispecies biofilms in biocorrosion are considered. The main approaches for protection of synthetic plastics from microbially caused damage are discussed. [ABSTRACT FROM AUTHOR]

Patterns of formation of three-species biofilms on the surface of an LDPE-based composite material were studied using a mixture of pure planktonic cultures of microorganisms capable of degrading this polymer. This is the first report of the role of the ascomycete Yarrowia lipolytica as a primary colonizer in this system, forming aggregates with gram-negative bacteria Pseudomonas aeruginosa or Chromobacterium violaceum. Addition of biocidal compounds of the guanidine family to LDPE as a component of the filler was shown to result in selective suppression of biofilm growth of some microorganisms, while it had no effect on the initial stages of adhesion and on planktonic growth of the cultures. Gram-positive bacteria of the genus Kocuria exhibited the highest sensitivity to these biocidal agents. [ABSTRACT FROM AUTHOR]

This study investigates the antibiofilm action of nitric oxide (NO)-releasing hyperbranched polymers against ex vivo multispecies periodontal biofilms. The antibiofilm efficacy of NO-releasing hyperbranched polymers was evaluated as a function of NO-release properties, polymer concentrations, and oxygen levels in the exposure media. 16s rRNA sequencing technique was employed to evaluate the impact of NO-releasing hyperbranched polymers on the microbial composition of the biofilms. The addition of NO release significantly improved the antibiofilm action of the hyperbranched polymers, with NO-releasing hyperbranched polyamidoamines of largest NO payloads being more effective than hyperbranched polykanamycins. Furthermore, the NO-releasing hyperbranched polymers reduced the biofilm metabolic activity in a dose-dependent manner, killing biofilm-detached bacteria under both aerobic and anaerobic conditions, with greater antimicrobial efficacy observed under aerobic conditions. These results demonstrate for the first time the potential therapeutic utility of NO-releasing hyperbranched polymers for treating multispecies dental biofilms. [ABSTRACT FROM AUTHOR]

The arrival order of different species to a habitat can strongly impact community assembly and succession dynamics, thus influencing functionality. In this study, we asked how prior colonization of one community member would influence the assembly of a synergistic multispecies biofilm community grown in vitro. We expected that the prior arrival would confer an advantage, in particular for good biofilm formers. Yet, we did not know if the cohabitants would be impaired or benefit from the pre-colonization of one member, depending on its ability to form biofilm. We used a consortium consisting of four soil bacteria; Stenotrophomonas rhizophila, Xanthomonas retroflexus, Microbacterium oxydans and Paenibacillus amylolyticus. This consortium has been shown to act synergistically when grown together, thus increasing biofilm production. The results showed that the two good biofilm formers gained a fitness advantage (increase in abundance) when allowed prior colonization on an abiotic surface before the arrival of their cohabitants. Interestingly, the significantly higher number of the pre-colonized biofilm formers did not affect the resulting composition in the subsequent biofilm after 24 h.

Salmonella enterica is a leading cause of foodborne illness in the U.S. In the meat industry, one action taken to address pathogen contamination incidence is an intense sanitization (IS) of the entire processing plant that many large processors perform annually or semiannually. However, this procedure's immediate and long-term impact on environment microbial community and pathogen colonization are unknown. Here we investigated the impact of IS procedure on environmental biofilms and the subsequent S. enterica colonization and stress tolerance. Environmental samples were collected from floor drains at various areas 1 week before, 1 week, and 4 weeks after the IS procedure at a beef plant with sporadic S. enterica prevalence. Biofilm formation by microorganisms in the drain samples without S. enterica presence was tested under processing temperature. The ability of the biofilms to recruit and/or protect a co-inoculated S. enterica strain from quaternary ammonium compound (QAC) treatment was determined. The community structure of each drain sample was elucidated through 16S rRNA amplicon community sequencing. Post-IS samples collected from 8 drains formed significantly stronger biofilms than the respective pre-IS samples. S. enterica colonization was not different between the pre- and post-IS biofilms at all drain locations. S. enterica survival in QAC-treated pre- and post-IS mixed biofilms varied depending upon the drain location but a higher survival was associated with a stronger biofilm matrix. The 16S rRNA amplicon gene community sequencing results exhibited a decrease in community diversity 1 week after IS treatment but followed by a significant increase 4 weeks after the treatment. The IS procedure also significantly altered the community composition and the higher presence of certain species in the post-IS community may be associated with the stronger mixed biofilm formation and Salmonella tolerance. Our study suggested that the IS procedure might disrupt the existing environmental microbial community and alter the natural population composition, which might lead to unintended consequences as a result of a lack of competition within the multispecies mixture. The survival and recruitment of species with high colonizing capability to the post-IS community may play crucial roles in shaping the ensuing ecological dynamics., Competing Interests: RW, MG, and JB were employed by U. S. Department of Agriculture. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright At least a portion of this work is authored by Rong Wang, Manita Guragain and Joseph M. Bosilevac on behalf of the U.S. Government and as regards Dr. Wang, Dr. Guragain, Dr. Bosilevac and the U.S. Government, is not subject to copyright protection in the United States. Foreign and other copyrights may apply.)

Microorganisms colonizing plant roots co-exist in complex, spatially structured multispecies biofilm communities. However, little is known about microbial interactions and the underlying spatial organization within biofilm communities established on plant roots. Here, a well-established four-species biofilm model (Stenotrophomonas rhizophila, Paenibacillus amylolyticus, Microbacterium oxydans, and Xanthomonas retroflexus, termed as SPMX) was applied to Arabidopsis roots to study the impact of multispecies biofilm on plant growth and the community spatial dynamics on the roots. SPMX co-culture notably promoted root development and plant biomass. Co-cultured SPMX increased root colonization and formed multispecies biofilms, structurally different from those formed by monocultures. By combining 16S rRNA gene amplicon sequencing and fluorescence in situ hybridization with confocal laser scanning microscopy, we found that the composition and spatial organization of the four-species biofilm significantly changed over time. Monoculture P. amylolyticus colonized plant roots poorly, but its population and root colonization were highly enhanced when residing in the four-species biofilm. Exclusion of P. amylolyticus from the community reduced overall biofilm production and root colonization of the three species, resulting in the loss of the plant growth-promoting effects. Combined with spatial analysis, this led to identification of P. amylolyticus as a keystone species. Our findings highlight that weak root colonizers may benefit from mutualistic interactions in complex communities and hereby become important keystone species impacting community spatial organization and function. This work expands the knowledge on spatial organization uncovering interspecific interactions in multispecies biofilm communities on plant roots, beneficial for harnessing microbial mutualism promoting plant growth., (© The Author(s) 2024. Published by Oxford University Press on behalf of the International Society for Microbial Ecology.)

This study investigated the microbial dynamics in multispecies biofilms of Escherichia coli O157:H7 strain 1934 (O157) or Salmonella enterica serovar Typhimurium ATCC 14028 (ST) and 40 strains of meat processing surface bacteria (MPB). Biofilms of O157 or ST with/without MPB were developed on stainless steel coupons at 15°C for up to 6 days. Bacteria in suspensions (inoculum, days 2 and 6) and biofilms (days 2 and 6) were enumerated by plating. The composition of multispecies cultures was determined by 16S rRNA gene sequencing. In suspensions, levels of O157 and ST were ~2 log higher in single-species than in multispecies cultures on both sampling days. ST was 3 log higher in single-species than in multispecies biofilms. A similar trend, though to a lesser extent, was observed for O157 in biofilms on day 2 but not on day 6. No difference (P >0.05) in bacterial counts was noted for the two MPB-pathogen cocultures at any time during incubation. Bacterial diversity in multispecies cultures decreased with incubation time, irrespective of the pathogen or culture type. The changes in the relative abundance of MPB were similar for the two MPB-pathogen cocultures, though different interbacterial interactions were noted. Respective fractions of ST and O157 were 2.1% and 0.97% initially and then 0.10% and 0.07% on day 2, and 0.60% and 0.04% on day 6. The relative proportions of facultative anaerobes in both multispecies cultures were greater in both suspensions and biofilms than in the inoculum. Citrobacter, Hafnia, Aeromonas, and Carnobacterium predominated in biofilms but not always in the planktonic cultures. [ABSTRACT FROM AUTHOR]

The arrival order of different species to a habitat can strongly impact community assembly and succession dynamics, thus influencing functionality. In this study, we asked how prior colonization of one community member would influence the assembly of a synergistic multispecies biofilm community grown in vitro. We expected that the prior arrival would confer an advantage, in particular for good biofilm formers. Yet, we did not know if the cohabitants would be impaired or benefit from the pre-colonization of one member, depending on its ability to form biofilm. We used a consortium consisting of four soil bacteria; Stenotrophomonas rhizophila, Xanthomonas retroflexus, Microbacterium oxydans and Paenibacillus amylolyticus. This consortium has been shown to act synergistically when grown together, thus increasing biofilm production. The results showed that the two good biofilm formers gained a fitness advantage (increase in abundance) when allowed prior colonization on an abiotic surface before the arrival of their cohabitants. Interestingly, the significantly higher number of the pre-colonized biofilm formers did not affect the resulting composition in the subsequent biofilm after 24 h. [ABSTRACT FROM AUTHOR]

Pathogens and spoilage microorganisms can develop multispecies biofilms on food contact surfaces; however, few studies have been focused on evaluated mixed biofilms of these microorganisms. Therefore this study investigated the biofilm development by pathogenic (Bacillus cereus , Escherichia coli , Listeria monocytogenes , and Salmonella enterica Enteritidis and Typhimurium serotypes) and spoilage (Bacillus cereus and Pseudomonas aeruginosa) microorganisms onto stainless-steel (SS) and polypropylene B (PP) coupons; under conditions that mimic the dairy, meat, and egg processing industry. Biofilms were developed in TSB with 10% chicken egg yolk (TSB + EY), TSB with 10% meat extract (TSB + ME) and whole milk (WM) onto SS and PP. Each tube was inoculated with 25 μL of each bacteria and then incubated at 9 or 25 °C, with enumeration at 1, 48, 120, 180 and 240 h. Biofilms were visualized by epifluorescence and scanning electron microscopy (SEM). Biofilm development occurred at different phases, depending on the incubation conditions. In the reversible adhesion, the cell density of each bacteria was between 1.43 and 6.08 Log 10 CFU/cm2 (p < 0.05). Moreover, significant reductions in bacteria appeared at 9 °C between 1 and 48 h of incubation. Additionally, the constant multiplication of bacteria in the biofilm occurred at 25 °C between 48 and 180 h of incubation, with increments of 2.08 Log 10 CFU/cm2 to S. Typhimurium. Population establishment was observed between 48 and 180 h and 180–240 h incubation, depending on the environmental conditions (25 and 9 °C, respectively). For example, in TSB + ME at 25 °C, S. Typhimurium, P aeruginosa , and L. monocytogenes showed no statistical differences in the amounts between 48 and 180 h incubation. The dispersion phase was identified for L. monocytogenes and B. cereus at 25 °C. Epifluorescence microscopy and SEM allowed visualizing the bacteria and extracellular polymeric substances at the different biofilm stages. In conclusion, pathogens and spoilage microorganisms developed monospecies with higher cellular densities than multiespecies biofilms. In multispecies biofilms, the time to reach each biofilm phase varied is depending on environmental factors. Cell count decrements of 1.12–2.44 Log 10 CFU/cm2 occurred at 48 and 240 h and were most notable in the biofilms developed at 9 °C. Additionally, cell density reached by each microorganism was different, P. aeruginosa and Salmonella were the dominant microorganisms in the biofilms while B. cereus showed the lower densities until undetectable levels. • Pseudomonas aeruginosa and Salmonella were the dominant microorganisms in biofilms. • Bacillus cereus showed the lower cell densities in the biofilms. • Cell density was higher in biofilms settled on polypropylene than on stainless steel. • Cell density was higher on biofilms developed at 25 °C than at 9 °C. • Desorption and dispersion phases were mainly observed in biofilms developed at 9 °C. [ABSTRACT FROM AUTHOR]

Ceramic roof tiles are widespread marketed building materials, rapidly colonized by microorganisms that form multispecies biofilms on their surface and play crucial roles in biodeterioration processes. Coating tiles with water repellents is a pervasive industrial strategy employed to prevent liquid water penetration and slow biodeterioration. Very few studies have examined the links between the characteristics of water-repellent coatings and biofilm colonization patterns. Our work aims to compare the effects of coating tiles with two common water repellents (siliconate and siloxane) on the growth of colonizing microbes. We combined in situ exposure of tiles for over six years and macroscopic and microscopic observations with in vitro biotests, relying on the use of algal and fungal models. Our data showed that (1) tiles coated with water repellents were macroscopically less colonized by lichens (2) a significant fungal biofilm development at the microscopic scale (3) water repellents had very contrasting effects on our model strains. These data reinforce the great interest for industry to conduct more studies linking the nature of the water repellents with the composition of colonizing multispecies biofilms. The long-term objective is to improve the available water repellents and better adapt their selection to the nature of microbial colonization.

An imbalance of homeostasis between the microbial communities and the host system leads to dysbiosis in oral micro flora. DMTU (1,3-di-m-tolyl-urea) is a biocompatible compound that was shown to inhibit Streptococcus mutans biofilm by inhibiting its communication system (quorum sensing). Here, we hypothesized that DMTU is able to inhibit multispecies biofilms. We developed a multispecies oral biofilm model, comprising an early colonizer Streptococcus gordonii, a bridge colonizer Fusobacterium nucleatum, and late colonizers Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans. We performed comprehensive investigations to demonstrate the effect of DMTU on planktonic cells and biofilms. Our findings showed that DMTU inhibits and disrupts multispecies biofilms without bactericidal effects. Mechanistic studies revealed a significant down regulation of biofilm and virulence-related genes in P. gingivalis. Taken together, our study highlights the potential of DMTU to inhibit polymicrobial biofilm communities and their virulence.

Staphylococcus aureus and Cutibacterium acnes are common representatives of the human skin microbiome. However, when these bacteria are organized in biofilm, they could be involved in several skin disorders such as acne or psoriasis. They inhabit in hollows of hair follicles and skin glands, where they form biofilms. There, they are continuously exposed to human hormones, including human natriuretic peptides (NUPs). We first observed that the atrial natriuretic peptide (ANP) and the C-type natriuretic peptide (CNP) have a strong effect S. aureus and C. acnes biofilm formation on the skin. These effects are significantly dependent on the aero-anaerobic conditions and temperature. We also show that both ANP and CNP increased competitive advantages of C. acnes toward S. aureus in mixed biofilm. Because of their temperature-dependent effects, NUPs appear to act as a thermostat, allowing the skin to modulate bacterial development in normal and inflammatory conditions. This is an important step toward understanding how human neuroendocrine systems can regulate the cutaneous microbial community and should be important for applications in fundamental sciences, medicine, dermatology, and cosmetology.

Lung disease in cystic fibrosis (CF) is characterized by the progressive colonization of the respiratory tract by different bacteria, which develop polymicrobial biofilms. In the past decades, there has been an increase in the number of CF patients infected with Non-Tuberculous Mycobacteria (NTM). Although Mycobacterium abscessus is the main NTM isolated globally, little is known about M. abscessus multispecies biofilm formation. In the present study we developed an in vitro model to study the phenotypic characteristics of biofilms formed by M. abscessus and Pseudomonas aeruginosa , a major pathogen in CF. For that purpose, dual species biofilms were grown on polycarbonate membranes with a fixed concentration of P. aeruginosa and different inoculums of M. abscessus. The biofilms were sampled at 24, 48, and 72 h and bacteria were quantified in specific media. The results revealed that the increasing initial concentration of M. abscessus in dual species biofilms had an effect on its population only at 24 and 48 h, whereas P. aeruginosa was not affected by the different concentrations used of M. abscessus . Time elapsed increased biofilm formation of both species, specially between 24 and 48 h. According to the results, the conditions to produce a mature dual species biofilm in which the relative species distribution remained stable were 72 h growth of the mixed microbial culture at a 1:1 ratio. A significant decrease in mycobacterial population in dual compared to single species biofilms was found, suggesting that P. aeruginosa has a negative influence on M. abscessus . Finally, in a proof of concept experiment, young and mature dual species biofilms were exposed to clarithromycin. [ABSTRACT FROM AUTHOR]

The work presents the qualitative analysis of the free boundary value problem related to the biosorption process in multispecies biofilms. In the framework of continuum biofilm modeling, the mathematical problem consists of a system of nonlinear hyperbolic partial differential equations for microbial species growth and spreading, a system of semilinear parabolic partial differential equations describing the substrate trends and a system of semilinear parabolic partial differential equations accounting for the diffusion, reaction and biosorption of different agents on the various biofilm constituents. Two systems of nonlinear hyperbolic partial differential equations have been considered as well for modeling the dynamics of the free and bounded sorption sites. The free boundary evolution is regulated by a nonlinear ordinary differential equation. Overall, this leads to a free boundary value problem essentially hyperbolic. The main result is the existence and uniqueness of the solutions to the stated free boundary value problem, which have been derived by converting the partial differential equations to Volterra integral equations and then using the fixed point theorem. Moreover, the work is completed with numerical simulations for a real case examining the growth of a heterotrophic–autotrophic biofilm devoted to wastewater treatment and acting as a sorbing material for heavy metal biosorption. [ABSTRACT FROM AUTHOR]