Biofilm Colonization Research Articles

Dynamics of drinking water biofilm formation associated with Legionella spp. colonization.

Understanding how Legionella spp. proliferate in multispecies biofilms is essential to develop strategies to control their presence in building plumbing. Here, we analyzed biofilm formation and Legionella spp. colonization on new plumbing material during 8 weeks. Biofilm formation was characterized by an initial increase in intact cell concentrations up to 9.5 × 105 cells/cm2, followed by a steady decrease. We identified Comamonas, Caulobacter, Schlegella, Blastomonas and Methyloversatilis as pioneer genera in the biofilm formation process. Importantly, L. pneumophila was the dominant Legionella spp. and rapidly colonized the biofilms, with culturable cell concentrations peaking at 3.1 × 104 MPN/cm2 after 4 weeks already. Moreover, several Legionella species co-occurred and had distinct dynamics of biofilm colonization. Vermamoeba vermiformis (V. vermiformis) was the dominant protist identified with 18S rRNA gene amplicon sequencing. Together our results highlight that biofilm formation upon introduction of new building plumbing material is a dynamic process where pathogenic Legionella species can be part of the earliest colonizers.

In Vitro Comparison of Titanium Disc Surface Roughness and Bacterial Colonization After Ultrasonic Instrumentation With Three Different Tips.

During implant maintenance, preserving a smooth surface on the machined transmucosal abutment is critical to reduce biofilm attachment and colonization. The present study compared the surface roughness and bacterial colonization of machined titanium surfaces after instrumentation with various materials. Forty-four machined grade 23 titanium discs were instrumented with a round polyether ether ketone (PEEK) tip, a plastic curette tip, or a pure titanium curette tip with piezoelectric devices. Before and after instrumentation, the surface roughness (Ra and Rz) values were analyzed with a profilometer and scanning electron microscopy (SEM). Streptococcus sanguinis was cultured and incubated for 24 hours on the instrumented discs, and colony-forming units per milliliter were obtained for each group. Samples instrumented with the metal ultrasonic tip significantly increased surface roughness compared with the other groups. This resulted in greater colonization by S. sanguinis than surfaces instrumented with PEEK tips or the negative control. Samples instrumented with PEEK and plastic tips did not exhibit any statistically significant increase in surface roughness, and SEM analysis revealed a significantly rougher surface of discs instrumented with metal compared with discs instrumented with plastic or PEEK tips despite the possibility of debris from tip dissolution. Our results suggest that instrumentation with metal ultrasonic tips with piezoelectric devices significantly increased machined titanium's surface roughness and elicited higher biofilm formation in vitro. Meanwhile, instrumentation of machined titanium with PEEK or plastic ultrasonic tips did not affect the surface roughness or bacterial adhesion.

Identification of Stutzerimonas stutzeri volatile organic compounds that enhance the colonization and promote tomato seedling growth.

Volatile organic compounds (VOCs) have an important function in plant growth-promoting rhizobacteria (PGPR) development and plant growth. This study aimed to identify VOCs of the PGPR strain, Stutzerimonas stutzeri NRCB010, and investigate their effects on NRCB010 biofilm formation, swarming motility, colonization, and tomato seedling growth. Solid-phase microextraction and gas chromatography-mass spectrometry were performed to identify the VOCs produced during NRCB010 fermentation. A total of 28 VOCs were identified. Among them, seven (e.g. γ-valerolactone, 3-octanone, mandelic acid, 2-heptanone, methyl palmitate, S-methyl thioacetate, and 2,3-heptanedione), which smell well, are beneficial for plant, or as food additives, and without serious toxicities were selected to evaluate their effects on NRCB010 and tomato seedling growth. It was found that most of these VOCs positively influenced NRCB010 swarming motility, biofilm formation, and colonization, and the tomato seedling growth. Notably, γ-valerolactone and S-methyl thioacetate exhibited the most positive performances. The seven NRCB010 VOCs, essential for PGPR and crop growth, are potential bioactive ingredients within microbial fertilizer formulations. Nevertheless, the long-term sustainability and replicability of the positive effects of these compounds across different soil and crop types, particularly under field conditions, require further investigation.

The activity of the quorum sensing regulator HapR is modulated by the bacterial extracellular vesicle (BEV)-associated protein ObfA of Vibrio cholerae.

Vibrio cholerae, a facultative human pathogen and causative agent of the severe diarrheal disease cholera, transits between the human intestinal tract and aquatic reservoirs. Like other bacterial species, V. cholerae continuously releases bacterial extracellular vesicles (BEVs) from its surface, which have been recently characterised for their role during in vivo colonisation. However, between epidemic outbreaks, V. cholerae persists in the biofilm mode for extended periods in aquatic reservoirs, which enhances environmental fitness and host transition. In this study, we investigated the effect of V. cholerae BEVs on biofilm formation, a critical feature for ex vivo survival. In contrast to BEVs from planktonic cultures, our results show that physiological concentrations of BEVs from dynamic biofilm cultures facilitate V. cholerae biofilm formation, which could be linked to a proteinaceous factor. Comparative proteomic analyses of planktonic- and biofilm-derived BEVs identified a previously uncharacterised outer membrane protein as an abundant component of dynamic biofilm-derived BEVs, which was found to be responsible for the BEV-dependent enhancement of biofilm production. Consequently, this protein was named outer membrane-associated biofilm facilitating protein A (ObfA). Comprehensive molecular studies unravelled ObfA as a negative modulator of HapR activity. HapR is a key transcriptional regulator of the V. cholerae quorum sensing (QS) cascade acting as a potent repressor of biofilm formation and virulence. Consistently, obfA mutants not only exhibited reduced biofilm production but also reduced colonisation fitness. Surprisingly, our results demonstrate that ObfA does not affect HapR through the canonical QS system but via the Csr-cascade altering the expression of the small regulatory RNAs CsrC and CsrD. In summary, this study elucidates a novel intraspecies BEV-based communication in V. cholerae that influences biofilm formation and colonisation fitness via a new regulatory pathway involving HapR, Csr-cascade and the BEV-associated protein ObfA.

Eco-friendly synthesis of Co3O4 nanoparticles using Millettia pinnata towards increased anti-oxidant, anti-biofilm and cytocompatibility properties against biofilm producing bacteria and human pulmonary alveolar basal cells

Biofilm architecture is an emerging threat worldwide due to enhanced antibiotic resistance against existing antibiotics, thus heightening the need to discover the alternative therapies that can eradicate the biofilm colonization. Current study highlights the eco-friendly, non-toxic nature of Co3O4 nanoparticles (NPs) using Millettia pinnata (M. pinnata) leaves extract and their application in anti-oxidants, anti-bacterial, anti-biofilm and cytocompatibilities. The GC-MS and FT-IR spectral data suggested that phytochemical derivatives of M. pinnata leaf extract simultaneously contributed in bio-reduction process and capping agent of Co3O4 NPs, which might be reason for anti-oxidant activities. Further, XRD analysis confirms the polycrystalline behaviour of Co3O4 NPs having hexagonal crystal system. FESEM, HRTEM, EDAX and elemental mapping revealed the formation of agglomerated granular shape along with nanorods on the surface of Co3O4 NPs, which confirms the presence of carbon and oxygen. Additionally, the characteristic band and thermal decomposition of Raman and TGA spectral data confirmed the molecular structure of Co3O4 NPs. Subsequently, both the M. pinnata leaves extract and Co3O4 NPs were found to be excellent source of antioxidants and produced significant DPPH and hydroxyl scavenging activities. Furthermore, the sub-biofilm inhibitory concentration of biosynthesized Co3O4 NPs reduced the biofilm growth in S. aureus and K. pneumoniae by crystal violet assay at increasing concentration. In addition, the membrane integrity of biofilm damages and architecture destruction was evidently proved due to the biosynthesized Co3O4 NPs by confocal laser scanning electron microscope and scanning electron microscope observation. Finally, the cytotoxicity experiment results indicated, biosynthesized Co3O4 NPs has no toxicity against human pulmonary alveolar epithelial cells at maximum concentration. Accordingly, findings of this study supported the utility of safety and efficiency of biosynthesized Co3O4 NPs against biofilm producing bacteria, and deserve as promising future drug discovery target for various bacterial infections.

Cobalt effects on prokaryotic communities of river biofilms: Impact on their colonization kinetics, structure and functions

Although cobalt (Co) plays a significant role in the transition to low-carbon technologies, its environmental impact remains largely unknown. This study examines Co impacts on the prokaryotic communities within river biofilms to evaluate their potential use as bioindicators of Co contamination. To this end, biofilms were cultivated in artificial streams enriched with different environmental Co concentrations (0.1, 0.5, and 1 μM Co) over 28 days and examined for prokaryotic abundance and diversity via quantitative PCR and DNA-metabarcoding every 7 days. The prokaryotic community's resilience was further investigated after an additional 35 days without Co contamination. The prokaryotic communities were affected by 0.5 and 1 μM Co from the onset of biofilm colonization. The biofilm biomass was comparable between treatments, but the community composition differed. Control biofilms were dominated by Cyanobacteria and Planctomycetes, whereas Bacteroidetes dominated the Co-contaminated biofilms. Potential functional redundancy was observed through the implementation of carbon fixation alternatives by non-photosynthetic prokaryotes in biofilms exposed to high Co concentrations. No structural resilience was observed in the biofilms after 35 days without Co contamination. Measuring the prokaryotic community structural response using molecular approaches appears to be a promising method for assessing shifts in water quality owing to Co contamination.

Microbial Colonization Pattern of Indwelling Double J Stents in Children.

Indwelling double-J-stent (DJ stent) kept post-urological procedures may cause urinary tract infections (UTIs) due to polymicrobial biofilm formation and colonisation. To determine the incidence and microbiological characteristics of DJ stent related UTIs in a paediatric population. Patients under the age of 18 admitted for DJ stent removal following pediatric urological procedures were enrolled into the study. Prior to surgical removal of the DJ stent, a urine sample was collected and the stent was cystoscopically removed under anesthesia. The ends of the stent were inoculated into culture media and incubated up to 48 hours. When growth was observed, an antibiogram was obtained using a panel of anti-microbial agents. The study group consisted of 27 patients (M: F = 23:4) with a mean age of 4.3 years (1 month - 13 years). The commonest indication for stent placement was Pyeloplasty, 19 (70%). Stent colonisation was found in 8 out of 27 patients (29.6%; CI 12-51%) and E.Coli (33%) was the commonest organism. Polymicrobial growth was noted in 4 patients. Organisms were sensitive to Cephaerazone/ Sulbactam and Amikacin, and resistant to other Cephalosporins. All 8 culture positive patients were asymptomatic and a repeat urine culture revealed no growth. Colonisation did not lead to active UTI and post stent removal the urine became sterile. Microbial colonisation was noted in 30% of patients with indwelling DJ stents. Prior knowledge of culture & sensitivity pattern helps to cover the patients with appropriate antibiotic on the day of stent removal.

Initiation of H1-T6SS dueling between Pseudomonas aeruginosa.

The Type VI secretion system (T6SS) is a multicomponent apparatus, present in many Gram-negative bacteria, which can inhibit bacterial prey in various ecological niches. Pseudomonas aeruginosa assembles one of its three T6SS (H1-T6SS) to respond to attacks from adjacent competing bacteria. Surprisingly, repeated assemblies of the H1-T6SS, termed dueling, were described in a monoculture in the absence of an attacker strain; however, the underlying mechanism was unknown. Here, we explored the role of H2-T6SS of P. aeruginosa in triggering H1-T6SS assembly. We show that H2-T6SS inactivation in P. aeruginosa causes a significant reduction in H1-T6SS dueling and that H2-T6SS activity directly triggers retaliation by the H1-T6SS. Intraspecific competition experiments revealed that elimination of H2-T6SS in non-immune prey cells conferred protection from H1-T6SS. Moreover, we show that the H1-T6SS response is triggered independently of the characterized lipase effectors of the H2-T6SS, as well as those of Acinetobacter baylyi and Vibrio cholerae. Our results suggest that H1-T6SS response to H2-T6SS in P. aeruginosa can impact intraspecific competition, particularly when the H1-T6SS effector-immunity pairs differ between strains, and could determine the outcome of multistrain colonization.IMPORTANCEThe opportunistic pathogen Pseudomonas aeruginosa harbors three different Type VI secretion systems (H1, H2, and H3-T6SS), which can translocate toxins that can inhibit bacterial competitors or inflict damage to eukaryotic host cells. Unlike the unregulated T6SS assembly in other Gram-negative bacteria, the H1-T6SS in P. aeruginosa is precisely assembled as a response to various cell damaging attacks from neighboring bacterial cells. Surprisingly, it was observed that neighboring P. aeruginosa cells repeatedly assemble their H1-T6SS toward each other. Mechanisms triggering this "dueling" behavior between sister cells were unknown. In this report, we used a combination of microscopy, genetic and intraspecific competition experiments to show that H2-T6SS initiates H1-T6SS dueling. Our study highlights the interplay between different T6SS clusters in P. aeruginosa, which may influence the outcomes of multistrain competition in various ecological settings such as biofilm formation and colonization of cystic fibrosis lungs.

Intraspecies interactions of Streptococcus mutans impact biofilm architecture and virulence determinants in childhood dental caries.

Early childhood dental caries (ECC) is the most common chronic disease among children, especially among low socioeconomic populations. Streptococcus mutans is most frequently associated with initiation of ECC. Although many studies report children with multiple S. mutans strains (i.e., genotypes) have greater odds of developing ECC, studies investigating intraspecies interactions in dental caries are lacking. This study investigates the impact of intraspecies interactions on cariogenic and fitness traits of clinical S. mutans isolates using in vitro and in vivo approaches. Association analysis evaluated if presence of multiple S. mutans genotypes within the first year of colonization was associated with caries. Initially, clinical S. mutans isolates from 10 children were evaluated. S. mutans strains (G09 and G18, most prevalent) isolated from one child were used for subsequent analysis. Biofilm analysis was performed for single and mixed cultures to assess cariogenic traits, including biofilm biomass, intra-polysaccharide, pH, and glucan. Confocal laser scanning microscopy (CLSM) and time-lapse imaging were used to evaluate spatial and temporal biofilm dynamics, respectively. A Drosophila model was used to assess colonization in vivo. Results showed the mean biofilm pH was significantly lower in co-cultured biofilms versus monoculture. Doubling of S. mutans biofilms was observed by CLSM and in vivo colonization in Drosophila for co-cultured S. mutans. Individual strains occupied specific domains in co-culture and G09 contributed most to increased co-culture biofilm thickness and colonization in Drosophila. Biofilm formation and acid production displayed distinct signatures in time-lapsed experiments. This study illuminates that intraspecies interactions of S. mutans significantly impacts biofilm acidity, architecture, and colonization.IMPORTANCEThis study sheds light on the complex dynamics of a key contributor to early childhood dental caries (ECC) by exploring intraspecies interactions of different S. mutans strains and their impact on cariogenic traits. Utilizing clinical isolates from children with ECC, the research highlights significant differences in biofilm architecture and acid production in mixed versus single genotype cultures. The findings reveal that co-cultured S. mutans strains exhibit increased cell density and acidity, with individual strains occupying distinct domains. These insights, enhanced by use of time-lapsed confocal laser scanning microscopy and a Drosophila model, offer a deeper understanding of ECC pathogenesis and potential avenues for targeted interventions.

Legionella colonization and 3D spatial location within a Pseudomonas biofilm

Biofilms are known to be critical for Legionella settlement in engineered water systems and are often associated with Legionnaire’s Disease events. One of the key features of biofilms is their heterogeneous three-dimensional structure which supports the establishment of microbial interactions and confers protection to microorganisms. This work addresses the impact of Legionella pneumophila colonization of a Pseudomonas fluorescens biofilm, as information about the interactions between Legionella and biofilm structures is scarce. It combines a set of meso- and microscale biofilm analyses (Optical Coherence Tomography, Episcopic Differential Interference Contrast coupled with Epifluorescence Microscopy and Confocal Laser Scanning Microscopy) with PNA-FISH labelled L. pneumophila to tackle the following questions: (a) does the biofilm structure change upon L. pneumophila biofilm colonization?; (b) what happens to L. pneumophila within the biofilm over time and (c) where is L. pneumophila preferentially located within the biofilm? Results showed that P. fluorescens structure did not significantly change upon L. pneumophila colonization, indicating the competitive advantage of the first colonizer. Imaging of PNA-labelled L. pneumophila showed that compared to standard culture recovery it colonized to a greater extent the 3-day-old P. fluorescens biofilms, presumably entering in VBNC state by the end of the experiment. L. pneumophila was mostly located in the bottom regions of the biofilm, which is consistent with the physiological requirements of both bacteria and confers enhanced Legionella protection against external aggressions. The present study provides an expedited methodological approach to address specific systematic laboratory studies concerning the interactions between L. pneumophila and biofilm structure that can provide, in the future, insights for public health Legionella management of water systems.

Colonization of construction materials by microbial flora of the oral cavity and its significance for prosthetics

Today there is no unified personalized approach to the selection of construction materials in orthopedic dentistry, hence it is necessary to introduce and further study the effect of construction materials on the microbiota of the oral cavity. In particular, principles of microbial adhesion to various construction materials, development of biofilm and bacterial colonization of concrete construction materials need to be analysed. The article provides a review of literature devoted to the description of the adhesive properties of oral microbiota to orthopedic materials from the groups of polymers, metals and ceramic constructions as well as the development of the negative impact of the construction material on the microbiota of a particular group of teeth and the general condition of the microflora of the oral cavity, increase of the risks of dental plaque formation, biofilms formation and a shift of microflora towards the predominance of cariogenic one.

Reviewing the role of microplastics as carriers for microorganisms in absorbing toxic trace elements.

The pervasive presence of microplastics in various settings, such as freshwater and marine ecosystems, has sparked serious concerns. Microplastics can operate as possible transporters for hazardous trace elements or microbes, even though they are not naturally able to actively absorb these compounds. The binding sites on the plastic's surface or the complexes that are formed with the organic material on the plastic are how this adsorption process takes place. Microplastics' surfaces also seem to be attractive to microorganisms, such as bacteria and algae. Microorganisms can adhere to the rough surface of microplastics, which facilitates their colonization and formation of biofilms. Numerous bacteria, including ones that have the ability to absorb hazardous trace elements, can be found in these biofilms. Microplastics and microbes can interact in ways that are advantageous and detrimental. Microplastics have the ability to act as a substrate for microbial growth, which could lead to an increase in the quantity of microorganisms in the surrounding environment. On the other hand, microplastics may make it easier for microbes to spread to new areas, which could help dangerous or deadly species proliferate. Research is still ongoing to determine the degree to which microplastics serve as carriers of microbes and hazardous trace elements. Comprehending the implications of microplastics, pollutants, and microorganisms in a variety of environmental conditions is difficult due to their complex interplay. This review provides a detailed description of the complexity of the problem and used the examples related to microplastics, its environmental effects, and impacts on human health.

Adhesion Forces of Dextran on Dental Materials as a Function of Contact Time and pH Value

The formation and colonization of biofilms inside the oral cavity are still not understood in detail, although biofilms inside the oral cavity can lead to expensive dental diseases like caries, periodontitis, or the detachment of implants. Such biofilms consist, to a large extent, of proteins, carbohydrates, and other macromolecules. Whereas the interaction of proteins with dental materials is widely studied, the literature does not report interactions of polysaccharides. Here, scanning force spectroscopy is used to investigate the adhesion forces of dextran as an abundant polysaccharide on different dental materials. The focus is dental titanium, accompanied by comparisons with dental gold and silicon as reference material. Different pH values and dental materials mimic representative conditions in the oral cavity. The main finding is that dextran adheres very well to dental materials, but with lower adhesion forces than proteins of similar mass, such as bovine serum albumin. As proteins, the adhesion forces increase with the contact time until a plateau is reached and the forces differ with the dental material. However, in contrast to proteins, pH does not play a role because dextran is uncharged over the measured range between pH 4.5 and pH 13.

Microbial colonization in the partially exposed nonabsorbable membrane during alveolar ridge preservation.

This study evaluated the impact of the partial exposition of the nonabsorbable membrane (dPTFE) on microbial colonization during bone healing. Patients indicated for tooth extraction were randomized to dPTFE group (n = 22) - tooth extraction and alveolar ridge preservation (ARP) using an intentionally exposed dPTFE membrane and USH group (n = 22) - tooth extraction and unassisted socket healing. Biofilm samples were collected at the barrier in the dPTFE and on the natural healing site in the USH after 3 and 28 days. Samples from the inner surface of the dPTFE barrier were also collected (n = 13). The microbiome was evaluated using the Illumina MiSeq system. Beta diversity was different from 3 to 28 days in both groups, and at 28 days, different microbial communities were identified between therapies. The dPTFE was characterized by a higher prevalence and abundance of gram-negative and anaerobic species than USH. Furthermore, the inner surface of the dPTFE membrane was colonized by a different community than the one observed on the outer surface. Intentionally exposed dPTFE membrane modulates microbial colonization in the ARP site, creating a more homogeneous and anaerobic community on the inner and outer surfaces of the membrane. DPTFE promoted faster biofilm colonization and enrichment of gram-negative and anaerobes close to the regenerated site in the membrane's inner and outer surfaces. dPTFE membrane can be used exposed to the oral site, but approaches for biofilm control should still be considered. The study was retrospectively registered at Clinicaltrials.gov (NCT04329351).

Responses of colonization and development of periphytic biofilms to three typical tire wear particles with or without incubation-aging in migrating aqueous phases

Understanding the behavior of tire wear particles (TWPs) and their impact on aquatic environments after aging is essential. This study explored the characteristics of TWPs generated using different methods (rolling friction, sliding friction, and cryogenic milling) and their transformation after exposure to environmental conditions mimicking runoff and sewage, focusing on their effects on river water and periphytic biofilms. Laboratory experiments indicate that at low exposure levels (0.1 mg/L), TWPs promoted biofilm growth, likely due to zinc release acting as a nutrient and the aggregation of particles serving as biofilm scaffolds. However, at higher concentrations (100 mg/L), TWPs inhibited biofilm development. This inhibition is linked to toxic byproducts like N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone and environmentally persistent free radicals, which reduce biofilm biomass, alter algal diversity, and decrease the production of essential biofilm components such as proteins and polysaccharides, consistent with the inhibitory behavior of TWPs on bis-(3′-5′)-cyclic diguanosine monophosphate and quorum sensing signals, including acyl-homoserine lactone and autoinducer-2. Aging processes, particularly after simulated sewage treatment, further affect ecological impacts of TWPs, reducing the benefits observed at low concentrations and intensifying the negative effects at high concentrations. Contribution of here lies in systematically revealing the impact of TWPs on the development of aquatic biofilms, emphasizing the logical relationship between their aging characteristics, environmental behavior, and ecological risks. It assesses not only the release effects of typical additives and conventional size effects but also highlights the emerging photochemical toxicity (persistent free radicals), thus providing valuable insights into the aquatic ecological risk assessment of TWPs.

Bisphenol A sorption on commercial polyvinyl chloride microplastics: Effects of UV-aging, biofilm colonization and additives on plastic behaviour in the environment.

Chemical additives are important components in commercial microplastics and their leaching behaviour has been widely studied. However, little is known about the potential effect of additives on the adsorption/desorption behaviour of pollutants on microplastics and their subsequent role as vectors for pollutant transport in the environment. In this study, two types of commercial polyvinyl chloride (PVC1 and PVC2) microplastics were aged by UV irradiation and biotic modification via biofilm colonization to investigate the adsorption and desorption behaviour of bisphenol A (BPA). Surface cracks and new functional groups (e.g., O–H) were found on PVC1 after UV irradiation, which increased available adsorption sites and enhanced H‒bonding interaction, resulting in an adsorption capacity increase from 1.28 μg/L to 1.85 μg/L. However, the adsorption and desorption capacity not showed significant changes for PVC2, which might be related to the few characteristic changes after UV aging with the protection of light stabilizers and antioxidants. The adsorption capacity ranged from 1.28 μg/L to 2.06 μg/L for PVC1 and PVC2 microplastics, and increased to 1.62 μg/L—2.95 μg/L after colonization by biofilms. The increased adsorption ability might be related to the N–H functional group, amide groups generated by microorganisms enhancing the affinity for BPA. The opposite effect was observed for desorption. Plasticizers can be metabolized during biofilm formation processes and might play an important role in microorganism colonization. In addition, antioxidants and UV stabilizers might also indirectly influence the colonization of microorganisms’ on microplastics by controlling the degree to which PVC microplastics age under UV. The amount of biomass loading on the microplastics would further alter the adsorption/desorption behaviour of contaminants. This study provides important new insights into the evaluation of the fate of plastic particles in natural environments.

In situ generating CO gas for destroying bacterial biofilms

The resistance and impermeability of bacterial biofilms lead to incurable infections. Interference with bacterial respiration is the key to the eradication of bacterial biofilm, but breaking the deep-tissue biofilm barrier to disrupt bacterial respiration still lacks effective means. Here, we report a hydrogel microsphere that disrupts bacterial respiration, supports in situ production of carbon monoxide gas (CO) to enhance the oxygen-depleted environment of biofilms and disrupts the bacterial respiratory chain, eliminating the bacterial biofilm ecotone (BRDMs). Under the specific interaction of α-helical structure and bacterial biofilm, BRDMs rapidly anchored and accumulated on the surface of bacterial biofilm within 8 h. Meanwhile, 8.64 μM CO gas was released in situ under an oxidative stress environment to deeply penetrate the biofilm and continuously destroy bacterial terminal oxidase, block bacterial respiration and finally disintegrate the biofilm. In a model of osteomyelitis, BRDMs disrupt the ecotopic colonization of MRSA biofilms in deep tissues, reduce inflammation, restore internal environmental homeostasis and accelerate tissue regeneration. BRDMs could be designed to remove drug-resistant biofilms from a wide range of deep tissues.

Microbial Biofilm Inhibition Using Magnetic Cross-Linked Polyphenol Oxidase Aggregates.

Microbial biofilm accumulation poses a serious threat to the environment, presents significant challenges to different industries, and exhibits a large impact on public health. Since there has not been a conclusive answer found despite various efforts, the potential green and economical methods are being focused on, particularly the innovative approaches that employ biochemical agents. In the present study, we propose a bio-nanotechnological method using magnetic cross-linked polyphenol oxidase aggregates (PPO m-CLEA) for inhibition of microbial biofilm including multidrug resistant bacteria. Free PPO solution showed only 55-60% biofilm inhibition, whereas m-CLEA showed 70-75% inhibition, as confirmed through microscopic techniques. The carbohydrate and protein contents in biofilm extracellular polymeric substances (EPSs) were reduced significantly. The m-CLEA demonstrated reusability up to 5 cycles with consistent efficiency in biofilm inhibition. Computational work was also done where molecular docking of PPO with microbial proteins associated with biofilm formation was conducted, resulting in favorable binding scores and inter-residual interactions. Overall, both in vitro and in silico results suggest that PPO interferes with microbial cell attachment and EPS formation, thereby preventing biofilm colonization.

An investigation into the effect of UV irradiation and biofilm colonization on adsorption and desorption behavior of polyurethane (PU) microplastics for bisphenol A (BPA)

Recent studies have demonstrated that microplastics (MPs) can act as a transport vector for pollutants in the environment. However, most studies have focused on carbon-carbon backbone polymers, with little known about heteroatom backbone polymers. In this study, polyurethane (PU) MPs were modified by UV irradiation and microorganism colonization to assess the different aging treatments on the interaction behavior (adsorption/desorption) between PU MPs and bisphenol A (BPA). The results of the adsorption kinetics experiment illustrated that the adsorption process of BPA could be described well by a pseudo-second order kinetic equation on both fresh and aged PU MPs. Although fresh PU MPs revealed the highest saturated adsorption capacity, at low BPA exposure concentrations (≤ 100 μg/L) the adsorption capacities for UV aged and biofilm colonized PU MPs were very similar to fresh MPs or even slightly higher than for fresh MPs, the main adsorption mechanisms including H-bonding interactions and π–π interactions. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) investigations suggested obvious physicochemical property changes (e.g., generation of new functional groups, erosion, etc.) after UV irradiation and biofilm colonization. This study also showed that different exposure environments (ultrapure water, artificial seawater, simulated gastric fluid) could affect BPA adsorption/desorption via hydrophobic and electrostatic interaction on PU surfaces. These results further clarify the adsorption mechanisms of BPA on PU MPs that have undergone different aging treatments, and provides a theoretical basis for the assessment of environmental behavior and exposure risks when PU MPs and BPA coexist.

Bacterial Communities on Degraded Prehistoric Rock Paintings in Maros-Pangkep Global Geopark

391 Bacterial Communities on Degraded Prehistoric Rock Paintings in Maros-Pangkep Global Geopark Nur Haedar1*, Muhammad Iqram1, Ambeng1, Yusriana2, Dody Priosambodo1, and Rustan Lebe3 1Biology Department, Faculty of Mathematics and Natural Sciences, Hasanuddin University, Makassar 90245 Indonesia 2Archaeology Department, Faculty of Cultural Science, Hasanuddin University, Makassar 90245 Indonesia 3Indonesian Heritage Agency, Ministry of Education, Culture, Research, and Technology, Jakarta 10110 Indonesia The Maros-Pangkep karst region is a natural landscape located inside the UNESCO Global Geopark, extending across two regencies in South Sulawesi. There are at least 135 prehistoric caves, of which about 78 of them still have traces of relics in the form of rock paintings. One thing that has made this region renowned is the presence of the world’s oldest ancient rock painting, ca. 40,000 years old, in an ancient cave. Unfortunately, many paintings have been experiencing degradation marked by color changes and exfoliation, which are thought to be partially caused by the colonization of bacterial biofilms. The present study, therefore, aimed to delineate the bacterial diversity of biofilms present in ancient rock paintings. Samples were collected from three different caves in the region and analyzed using Oxford Nanopore Technology, sequencing the full-length 16S rRNA gene (V1–V9 regions). The results showed that Firmicutes was the dominant bacterial taxon in both Leang Jing and Leang Parewe, representing 95 and 82% of the total bacterial community, respectively. In Leang Bulu Sipong, we observed a high relative abundance of both Betaproteobacteria (30%) and Firmicutes (44%). Among the taxa detected, some genera – including Cupriavidus, Bacillus, Lysinibacillus, Paenibacillus, Geobacillus, and Pseudomonas – are linked to the carbonate precipitation and rock weathering, which could give a clue on the role of bacterial activities in corroborating the biodegradation on the ancient rock arts. Despite the result of microbial diversity in the rock paintings, it is necessary to do further study on the mechanism of degradation performed by the bacteria. This will support the effort of local authorities to conserve local heritage aged a thousand years.