Abiotic Substrates Research Articles

Mussel Foot Protein-Inspired Adhesive Tapes with Tunable Underwater Adhesion.

Instant and strong adhesion to underwater adherends is a big challenge due to the continuous interference of water. Mussel foot protein-bioinspired catechol-based adhesives have garnered great interest in addressing this issue. Herein, a novel self-made catecholic compound with a long aliphatic chain was utilized to prepare thin (∼0.07 mm) and optically transparent (>80%) wet/underwater adhesive tapes by UV-initiated polymerization. Its adhesion activity was water-triggered, fast (<1 min), and strong (adhesion strength to porcine skin: ∼1.99 MPa; interfacial toughness: ∼610 J/m2, burst pressure: ∼1950 mmHg). The effect of the catechol/phenol group and positively charged moiety on the wet/underwater adhesion to abiotic/biotic substrates was investigated. On the wet/underwater adherends, the tape with catechol groups presented much higher interfacial toughness, adhesion strength, and burst pressure than the analogous tape with phenol groups. The tape with both the catechol group and cationic polyelectrolyte chitosan had a more impressive improvement in its adhesion to wet/underwater biological tissues than to abiotic substrates. Therefore, catechol and a positive moiety in the tape would synergistically enhance its wet/underwater adhesion to various substrates, especially to biological tissues. The instant, strong, and noncytotoxic tape may provide applications in underwater adhesion for sealing and wound closure.

Adhesion and biofilm formation by two clinical isolates of Trichosporon Cutaneum in various environmental conditions.

Trichosporon spp. is an emerging opportunistic pathogen and a common cause of both superficial and invasive infections. Although Trichosporon asahii is the most frequently isolated species, Trichosporon cutaneum is also widely observed, as it is the predominant agent in cases of white Piedra and onychomycosis. Trichosporon spp. is a known to produce biofilms, which serve as one of its virulence mechanisms, however, there is limited data available on biofilms formed by T. cutaneum. Thus, the aim of this study was to assess the adhesion and biofilm formation of two clinical isolates of T. cutaneum under various environmental conditions (including temperature, nutrient availability, and carbon source), as well as their tolerance to fluconazole. Adhesion was tested on common abiotic substrates (such as silicone, glass, and stainless steel), revealing that T. cutaneum readily adhered to all surfaces tested. CV staining was applied for the evaluation of the environment influence on biofilm efficiency and it was proved that the nutrient availability has a major impact. Additionaly, fluorescent staining was employed to visualize the morphology of T. cutaneum biofilm and its survival in the presence of fluconazole. Hyphae production was shown to play a role in elevated biofilm production in minimal medium and increased tolerance to fluconazole.

On-Site Formation of Functional Dopaminergic Presynaptic Terminals on Neuroligin-2-Modified Gold-Coated Microspheres.

Advancements in neural interface technologies have enabled the direct connection of neurons and electronics, facilitating chemical communication between neural systems and external devices. One promising approach is a synaptogenesis-involving method, which offers an opportunity for synaptic signaling between these systems. Janus synapses, one type of synaptic interface utilizing synaptic cell adhesion molecules for interface construction, possess unique features that enable the determination of location, direction of signal flow, and types of neurotransmitters involved, promoting directional and multifaceted communication. This study presents the first successful establishment of a Janus synapse between dopaminergic (DA) neurons and abiotic substrates by using a neuroligin-2 (NLG2)-mediated synapse-inducing method. NLG2 immobilized on gold-coated microspheres can induce synaptogenesis upon contact with spatially isolated DA axons. The induced DA Janus synapses exhibit stable synaptic activities comparable to that of native synapses over time, suggesting their suitability for application in neural interfaces. By calling for DA presynaptic organizations, the NLG2-immobilized abiotic substrate is a promising tool for the on-site detection of synaptic dopamine release.

Origin and paleoenvironmental significance of Al-rich glauconite in the Ediacaran/Cambrian deposits of the Lublin Basin, Poland (SW margin of Baltica)

Geochemical and mineralogical analyses of glauconite from formations deposited at the Ediacaran – Cambrian boundary along the SW margin of Baltica, integrated with sedimentological characteristics of its host-rocks, are discussed in the study. SEM-EDS and XRD studies indicate evolved to a highly evolved stage of maturation of glauconitic grains, i.e. they are characterized by a high K2O content (>6,5%) and only a small amount of smectite within an ordered R > 1 glauconite-smectite (G-S) mixed layered structure. Despite its high K2O content, glauconite shows a low Fe2O3 and high A2O3 content. Such chemical composition is distinctive for Precambrian glauconites that originated from abiotic substrates. We have identified glauconite in fractures of K-feldspar and quartz, indicating that at least some of the evolved/highly evolved glauconite grains have been formed by the replacement of these minerals. We have also recognized a new type of substrate, i.e. clay coatings, which has not been reported in previous publications on glauconite. In our opinion, the green grains characterized by cleavage and higher-order birefringence, usually described as vermicular glauconite, result from glauconitization of clay coatings, rather than biotite or muscovite flakes as previously thought. Clay coatings composed of 2:1 clay minerals, mostly smectites, represent natural parent material for initiation of G-S evolution that does not require considerable structural changes as in case of biotite or muscovite.Results of glauconite investigation compiled with the sedimentary record of the Ediacaran – Cambrian succession of the Lublin Basin allow us to reconstruct the environment of glauconite formation and its subsequent history. Glauconite occurs in quartzitic sandstones that show evidence of deposition in shallow marine, high-energy environments (barrier islands, tidal flats and shoreface), but reveals widespread transport. It was formed in a lagoon environment, which, on the one hand, was an area with a relatively stable sedimentation rate compared to concurrent estuaries or tidal flats, and on the other hand, was close to the area of source material that provided detrital substrates, i.e., feldspars and clay coatings, formed in clay-rich soil horizons on river terrace or delta sediments. The latter substrate appears to be an essential indicator of the environment of glauconite formation, which may occur in close proximity to a river mouth or an actively eroded coastline.

Halotolerant bacterial biofilms for desalination and water treatment: a pilot study.

Salinity has a significant impact on the water quality and crop yield. Physical desalination techniques were once thought to be expensive and time-consuming. Among biological techniques, halotolerant bacteria were thought to be the fastest and most effective way to reduce the salt content in brackish saltwater water. In the current study, halotolerant bacterial biofilms were used to desalinate saline water on abiotic substrates (such as sand, pebbles, glass beads, and plastic beads), and studied subsequently for the effects on Zea mays germination. Briefly, salt samples (SLT7 and SLT8) from the Khewra site in Punjab, Pakistan, as well as seawater and sea sand samples (USW1, USW3, USW6, DSW1, DSW4, SS1, and SS3) from Karachi, Sindh, Pakistan's Arabian Sea, were collected. Halotolerant bacteria were isolated and characterized. Crystal violet ring assays and capsule staining were used to estimate extracellular polymeric substance (EPS) and biofilm development, respectively. All halotolerant bacterial strains were spore formers and produced EPS and formed biofilms well. 16S rRNA gene sequencing of the best halotolerant bacteria, USW6, showed the closest (100%) similarity to Bacillus aerius strain G-07 (a novel species) (accession number ON202984). A pilot-scale experiment for desalinating the artificial water (supplemented with 1M NaCl) using biofilm adhered abiotic beads showed declined level of NaCl from 1M to 0.00003M after 15days in treated water. Also, Zea mays germination was observed in the plants using treated water compared to no growth in the non-treated saline water. Estimations of chlorophyll, total soluble sugar, and protein revealed that plants cultivated using elute collected from a desalinated pilot scale setup contained less chlorophyll (i.e., 5.994 and 116.76). Likewise, plants grown with elute had a total soluble protein and sugar content of 1.45mg/ml and 1.3mg/ml, respectively. Overall, in treated water plants, a minor drop in chlorophyll content, a slight increase in total soluble sugar content, and a slight increase in protein content were noted. The study concluded that biofilm-treated desalt water has the potential to significantly reduce the effects of droughts, soil salinization, and economic and environmental issues associated with agricultural drainage. The results specified the application of halotolerant bacteria biofilms (Bacillus aerius, a novel species, USW6) for water desalination to overcome the problem of water scarcity caused by global warming and the increased salinity.

A heptadeca amino acid peptide subunit of cathelicidin LL-37 has previously unreported antifungal activity.

Yeasts such as Candida albicans, albeit being ubiquitous members of the skin, oral and vaginal microbiome, can cause superficial to life-threatening infections. Human cathelicidin LL-37-based peptides have antibacterial activity and yet, their antifungal activity remains to be thoroughly characterized. The aim of this study was to comprehensively investigate the activity of LL-37-based peptides against C. albicans. LL-37 and its derivatives were tested for their ability to kill C. albicans planktonic cells in the presence of various biological matrices (serum, plasma, saliva and urine), that have been reported to inactivate peptides. The antibiofilm activity, resistance development and biocompatibility were investigated for the lead peptide. GK-17, a 17 amino acid peptide, showed remarkable stability to fungal aspartyl proteases and rapidly killed planktonic C. albicans despite the presence of biological matrices. GK-17 also inhibited adhesion to biotic and abiotic substrates, inhibited biofilm formation and eradicated preformed biofilms in the presence of biological matrices. Compared to nystatin, GK-17 had a lower propensity to allow for resistance development by C. albicans. The peptide showed concentration-dependent biocompatibility to red blood cells, with only 30% hemolysis even at 4× the fungicidal concentration. Taken together, GK-17 is a novel antifungal peptide with promising effects against C. albicans.

Conservation of cholera vibrios in complex microcosm containing green microalgae

BACKGROUND: In the summer-autumn period, the peak of phytoplankton reproduction and flowering occurs and results in the deterioration of the quality of river water is noted. At the same time, cases of gastrointestinal diseases in humans are recorded, and epidemic complications of cholera may occur in endemic areas. V. cholerae form biofilm on the surface of chitinous hydrobionts and plastic components can lead to the spread of V. cholerae, possibly explaining the autochthonous mechanism of their existence in water bodies.&#x0D; AIM: This study determines the duration of Vibrio cholerae preservation on biotic (chitin) and abiotic (plastic) substrates in the presence of green unicellular algae with a change in cultivation temperature under experimental conditions.&#x0D; MATERIALS AND METHODS: This study used bacteriological and molecular genetic methods to achieve its goal.&#x0D; RESULTS: The preservation of toxigenic and non-toxigenic strains of V. cholerae O1 El Tor and V. cholerae O139 (ctxАВ+tcpА+csh1 and ctxАtcpАcsh1+) for six months, including three months at a low temperature simulating the autumn-winter period, as part of biofilms in microcosms, where one component is green microalgae. We noted an excess of the concentration of V. cholerae O1 and O139 serogroups by two orders of magnitude in samples where one of the components is chitin and the reproduction of green microalgae in the presence of a chitin substrate. This is probably one stage in the food chain in the ecology of water bodies and, accordingly, can be a reservoir for biofilm forms of cholera vibrios. Preservation of V. cholerae O1 El Tor non-toxigenic strain in a viable state in biofilm samples on plastic at decreased temperatures 82C for three months is possibly due to the presence of a cold shock gene in its genome.&#x0D; CONCLUSION: Without a substrate for adhesion, colonization, and biofilm formation, vibrios are incapable of long-term persistence at low temperatures.

Cell Density-Regulated Adhesins Contribute to Early Disease Development and Adhesion in Ralstonia solanacearum.

Adhesins (adhesive proteins) help bacteria stick to and colonize diverse surfaces and often contribute to virulence. The genome of the bacterial wilt pathogen Ralstonia solanacearum (Rs) encodes dozens of putative adhesins, some of which are upregulated during plant pathogenesis. Little is known about the role of these proteins in bacterial wilt disease. During tomato colonization, three putative Rs adhesin genes were upregulated in a ΔphcA quorum-sensing mutant that cannot respond to high cell densities: radA (Ralstonia adhesin A), rcpA (Ralstonia collagen-like protein A), and rcpB. Based on this differential gene expression, we hypothesized that adhesins repressed by PhcA contribute to early disease stages when Rs experiences a low cell density. During root colonization, Rs upregulated rcpA and rcpB, but not radA, relative to bacteria in the stem at mid-disease. Root attachment assays and confocal microscopy with ΔrcpA/B and ΔradA revealed that all three adhesins help Rs attach to tomato seedling roots. Biofilm assays on abiotic surfaces found that Rs does not require RadA, RcpA, or RcpB for interbacterial attachment (cohesion), but these proteins are essential for anchoring aggregates to a surface (adhesion). However, Rs did not require the adhesins for later disease stages in planta, including colonization of the root endosphere and stems. Interestingly, all three adhesins were essential for full competitive fitness in planta. Together, these infection stage-specific assays identified three proteins that contribute to adhesion and the critical first host-pathogen interaction in bacterial wilt disease. IMPORTANCE Every microbe must balance its need to attach to surfaces with the biological imperative to move and spread. The high-impact plant-pathogenic bacterium Ralstonia solanacearum can stick to biotic and abiotic substrates, presumably using some of the dozens of putative adhesins encoded in its genome. We confirmed the functions and identified the biological roles of multiple afimbrial adhesins. By assaying the competitive fitness and the success of adhesin mutants in three different plant compartments, we identified the specific disease stages and host tissues where three previously cryptic adhesins contribute to success in plants. Combined with tissue-specific regulatory data, this work indicates that R. solanacearum deploys distinct adhesins that help it succeed at different stages of plant pathogenesis.

Habitat and river riparian assessment in the Hyrcanian Forest Ecoregion in Iran: providing basic information for the river management andrehabilitation.

The Hyrcanian Forest holds broad leaf forest remnants dating back to the early Cenozoic Era, which once covered a vast area of the North Temperate Zone. Today, many rivers within this region have been altered by human activities and urgently need rehabilitation. In this regard, 35 wadeable rivers including 14 reference and impacted sites were investigated to determine how different human pressures altered riverine landscapes and habitats. Hence, five common human pressures (agriculture, urbanization, aquaculture, dams, aggregate mining) were identified, then the riverine landscape and habitat condition of each site were assessed. At each site, 17 aquatic, riparian, and terrestrial features, including abiotic and biotic substrate types, were investigated. The number and ratio of pressure-influenced channel features and substrate types differed from those in reference sites. Reference sites were dominated by microlithal, mesolithal, and macrolithal abiotic substrates and large wood, algae, and coarse particulate organic matter biotic substrates. Urbanized sites were most altered and dominated by single channels, steep unvegetated riprap banks, and algae substrate. The results provide valuable information for managers and decision-makers to restore riverine ecosystems considering the impaired parameters resulting from human pressures.

Universal and Stable Slippery Coatings: Chemical Combination Induced Adhesive-Lubricant Cooperation.

Liquid lubricant of low affinity makes slippery coatings widely used in lubricating, anti-biofouling, anti-icing, fluid guiding, and drag reduction. Two critical challenges, however, remain in the practical application of slippery coatings consisting of liquid lubricants: (1) universality regardless of roughness and chemical composition of substrates, (2) stability of surface lubricity against evaporation. Herein, a chemical method is reported to create a universal and stable slippery lubricant-adhesive cooperated coating (SLACC) through acid catalyzed dehydration reaction between the phenolic hydroxyl of polydopamine (PDA), with universal (for challenge-1) and strong (for challenge-2) adhesion properties, and liquid-like polydimethylsiloxane (PDMS), with lubricant properties. Through overlying PDMS on PDA, a spatial gradient interpenetration of chemical combined PDA and PDMS leaving lubricant PDMS at the outermost of coating is achieved. This structure contributes to the following performances of SLACC: nearly universality suitable for 100 different abiotic or biotic substrates and stability sustainable for long-term usages, UV radiating, refrigerating, hot air drying, freeze drying, knife scratch and abrasion. This proposed strategy is envisioned anti-fouling from plane to tube and exhibits drag reduction in confined space.

Structure and Conservation of Amyloid Spines From the Candida albicans Als5 Adhesin.

Candida Als family adhesins mediate adhesion to biological and abiotic substrates, as well as fungal cell aggregation, fungal-bacterial co-aggregation and biofilm formation. The activity of at least two family members, Als5 and Als1, is dependent on amyloid-like protein aggregation that is initiated by shear force. Each Als adhesin has a ∼300-residue N-terminal Ig-like/invasin region. The following 108-residue, low complexity, threonine-rich (T) domain unfolds under shear force to expose a critical amyloid-forming segment 322SNGIVIVATTRTV334 at the interface between the Ig-like/invasin domain 2 and the T domain of Candida albicans Als5. Amyloid prediction programs identified six potential amyloidogenic sequences in the Ig-like/invasin region and three others in the T domain of C. albicans Als5. Peptides derived from four of these sequences formed fibrils that bound thioflavin T, the amyloid indicator dye, and three of these revealed atomic-resolution structures of cross-β spines. These are the first atomic-level structures for fungal adhesins. One of these segments, from the T domain, revealed kinked β-sheets, similarly to LARKS (Low-complexity, Amyloid-like, Reversible, Kinked segments) found in human functional amyloids. Based on the cross-β structures in Als proteins, we use evolutionary arguments to identify functional amyloidogenic sequences in other fungal adhesins, including adhesins from Candida auris. Thus, cross-β structures are often involved in fungal pathogenesis and potentially in antifungal therapy.

Effect of Bacteriocin (ALC102) of Enterococcus faecium GRD AA on Biofilm Forming Listeria monocytogenes MTCC 657

Antilisterial bacteriocin producing strain were isolated from milk samples and were subjected to 16S rRNA sequencing and found to be of genus Enterococcus faecium. The bacteriocin ALC102 were partially purified by Amberlite XAD-16 adsorption followed by column chromatography. The biofilm formation capacity of Listeria monocytogenes MTCC 657 were evaluated by tube method and CV binding assay. Biofilm formation on different abiotic substrates were also evaluated. Among three substrates stainless steel had a strong biofilm formation followed by glass and aluminum foil. From the results of biofilm eradication studies, the bacteriocin ALC102 showed almost similar activity of commercial bacteriocin nisin on all the substrates at 45°C, 30°C, 4°C and -20°C. Based on CBD® biofilm eradication assay, the eradication potential of ALC102 and nisin were found to be similar on high (45°C) and freezing (-20°C) temperatures. From the study, antilisterial bacteriocin ALC102 found to be able to inhibit the biofilm formed Listeria monocytogenes MTCC 657 at different temperatures and different incubation periods (24h, 48h and 72h). The biofilm eradication potential of antilisterial bacteriocin ALC102 was similar to nisin. Neither incubation temperature nor incubation period doesn’t altered the activity of the bacteriocin. So this bacteriocin can be considered as a potential competitor in food industry and we strongly recommend the use of this bacteriocin from Enterococcus faecium GRD AA in the food preservation industry to a higher temperature (45°C) to freezing temperature (-20°C).

Assessment of organic substrates as sites for zebra mussel (Dreissena polymorpha) attachment in four West-Central Minnesota Lakes

Zebra mussels (Dreissena polymorpha) are an aquatic invasive species generalist with known ecological and economic impacts due to their settlement and attachment characteristics as well as their filtration abilities. Although zebra mussel attachment to abiotic substrates has been extensively studied, the importance of organic substrates for established zebra mussel populations in North American waters has not been evaluated. We assessed organic substrates in four west-central Minnesota lakes. Using qualitative analysis, we found most substrates were used proportionally to their availability. A quantitative assessment revealed significantly more zebra mussels attached to detritus than pondweeds (P < 0.05). Algae (filamentous and Chara spp.) were a significant suitable substrate for zebra mussel attachment (P < 0.05). Furthermore, more juvenile zebra mussels were found on organic substrates than were adults (P < 0.001). Although not always a consistent substrate, biological material as a vector for zebra mussel spread and settlement should be considered in further research to mitigate subsequent invasions and manage already naturalized populations.

Surface Properties of Parabacteroides distasonis and Impacts of Stress-Induced Molecules on Its Surface Adhesion and Biofilm Formation Capacities.

The gut microbiota is a complex and dynamic ecosystem whose balance and homeostasis are essential to the host’s well-being and whose composition can be critically affected by various factors, including host stress. Parabacteroides distasonis causes well-known beneficial roles for its host, but is negatively impacted by stress. However, the mechanisms explaining its maintenance in the gut have not yet been explored, in particular its capacities to adhere onto (bio)surfaces, form biofilms and the way its physicochemical surface properties are affected by stressing conditions. In this paper, we reported adhesion and biofilm formation capacities of 14 unrelated strains of P. distasonis using a steam-based washing procedure, and the electrokinetic features of its surface. Results evidenced an important inter-strain variability for all experiments including the response to stress hormones. In fact, stress-induced molecules significantly impact P. distasonis adhesion and biofilm formation capacities in 35% and 23% of assays, respectively. This study not only provides basic data on the adhesion and biofilm formation capacities of P. distasonis to abiotic substrates but also paves the way for further research on how stress-molecules could be implicated in P. distasonis maintenance within the gut microbiota, which is a prerequisite for designing efficient solutions to optimize its survival within gut environment.

Priority effects dictate community structure and alter virulence of fungal-bacterial biofilms

Polymicrobial biofilms are a hallmark of chronic wound infection. The forces governing assembly and maturation of these microbial ecosystems are largely unexplored but the consequences on host response and clinical outcome can be significant. In the context of wound healing, formation of a biofilm and a stable microbial community structure is associated with impaired tissue repair resulting in a non-healing chronic wound. These types of wounds can persist for years simmering below the threshold of classically defined clinical infection (which includes heat, pain, redness, and swelling) and cycling through phases of recurrent infection. In the most severe outcome, amputation of lower extremities may occur if spreading infection ensues. Here we take an ecological perspective to study priority effects and competitive exclusion on overall biofilm community structure in a three-membered community comprised of strains of Staphylococcus aureus, Citrobacter freundii, and Candida albicans derived from a chronic wound. We show that both priority effects and inter-bacterial competition for binding to C. albicans biofilms significantly shape community structure on both abiotic and biotic substrates, such as ex vivo human skin wounds. We further show attachment of C. freundii to C. albicans is mediated by mannose-binding lectins. Co-cultures of C. freundii and C. albicans trigger the yeast-to-hyphae transition, resulting in a significant increase in neutrophil death and inflammation compared to either species alone. Collectively, the results presented here facilitate our understanding of fungal-bacterial interactions and their effects on host-microbe interactions, pathogenesis, and ultimately, wound healing.

Micellar catalysis of the Suzuki Miyaura reaction using biogenic Pd nanoparticles from Desulfovibrio alaskensis.

Microorganisms produce metal nanoparticles (MNPs) upon exposure to toxic metal ions. However, the catalytic activity of biosynthesised MNPs remains underexplored, despite the potential of these biological processes to be used for the sustainable recovery of critical metals, including palladium. Herein we report that biogenic palladium nanoparticles generated by the sulfate-reducing bacterium Desulfovibrio alaskensis G20 catalyse the ligand-free Suzuki Miyaura reaction of abiotic substrates. The reaction is highly efficient (>99% yield, 0.5 mol% Pd), occurs under mild conditions (37 °C, aqueous media) and can be accelerated within biocompatible micelles at the cell membrane to yield products containing challenging biaryl bonds. This work highlights how native metabolic processes in anaerobic bacteria can be combined with green chemical technologies to produce highly efficient catalytic reactions for use in sustainable organic synthesis.

Interactions between Candida albicans and Enterococcus faecalis in an Organotypic Oral Epithelial Model.

Candida albicans as an opportunistic pathogen exploits the host immune system and causes a variety of life-threatening infections. The polymorphic nature of this fungus gives it tremendous advantage to breach mucosal barriers and cause oral and disseminated infections. Similar to C. albicans, Enterococcus faecalis is a major opportunistic pathogen, which is of critical concern in immunocompromised patients. There is increasing evidence that E. faecalis co-exists with C. albicans in the human body in disease samples. While the interactive profiles between these two organisms have been studied on abiotic substrates and mouse models, studies on their interactions on human oral mucosal surfaces are non-existent. Here, for the first time, we comprehensively characterized the interactive profiles between laboratory and clinical isolates of C. albicans (SC5314 and BF1) and E. faecalis (OG1RF and P52S) on an organotypic oral mucosal model. Our results demonstrated that the dual species biofilms resulted in profound surface erosion and significantly increased microbial invasion into mucosal compartments, compared to either species alone. Notably, several genes of C. albicans involved in tissue adhesion, hyphal formation, fungal invasion, and biofilm formation were significantly upregulated in the presence of E. faecalis. By contrast, E. faecalis genes involved in quorum sensing, biofilm formation, virulence, and mammalian cell invasion were downregulated. This study highlights the synergistic cross-kingdom interactions between E. faecalis and C. albicans in mucosal tissue invasion.

Effects of substratum and depth on benthic harmful dinoflagellate assemblages

Microhabitats influence the distribution and abundance of benthic harmful dinoflagellate (BHAB) species. Currently, much of the information on the relationships between BHABs and microhabitat preferences is based on non-quantitative anecdotal observations, many of which are contradictory. The goal of this study was to better quantify BHAB and microhabitat relationships using a statistically rigorous approach. Between April 2016 to May 2017, a total of 243 artificial substrate samplers were deployed at five locations in the Perhentian Islands, Malaysia while simultaneous photo-quadrat surveys were performed to characterize the benthic substrates present at each sampling site. The screen samplers were retrieved 24 h later and the abundances of five BHAB genera, Gambierdiscus, Ostreopsis, Coolia, Amphidinium, and Prorocentrum were determined. Substrate data were then analyzed using a Bray–Curtis dissimilarity matrix to statistically identify distinct microhabitat types. Although BHABs were associated with a variety of biotic and abiotic substrates, the results of this study demonstrated differing degrees of microhabitat preference. Analysis of the survey results using canonical correspondence analysis explained 70.5% (horizontal first axis) and 21.6% (vertical second axis) of the constrained variation in the distribution of various genera among microhabitat types. Prorocentrum and Coolia appear to have the greatest range being broadly distributed among a wide variety of microhabitats. Amphidinium was always found in low abundances and was widely distributed among microhabitats dominated by hard coral, turf algae, sand and silt, and fleshy algae and reached the highest abundances there. Gambierdiscus and Ostreopsis had more restricted distributions. Gambierdiscus were found preferentially associated with turf algae, hard coral and, to a lesser extent, fleshy macroalgae microhabitats. Ostreopsis, almost always more abundant than Gambierdiscus, preferred the same microhabitats as Gambierdiscus and were found in microbial mats as well. With similar habitat preferences Ostreopsis may serve as an indicator organism for the presence of Gambierdiscus. This study provides insight into how BHAB-specific microhabitat preferences can affect toxicity risks.

Study of biofilms by V. cholerae strains on the surfaces of biotic and abiotic substrates using mass spectrometry

Objective: identification and comparative study of protein spectra of Vibrio cholerae biofilms by MALDI-ToF mass spectrometry.Materials and methods: V. cholerae O1 strains isolated from different sources were studied. Methods: bacteriological, mass spectrometry.Results: mass spectrometric analysis showed that it was impossible to identify strains from “plankton” samples and from chitin and plastic plates. After culturing the biofilm and plankton strains, all of them were assigned to the V. cholerae species with a Score above 2,300. A сomparative analysis of MALDI-ToF mass spectra of different variants of V. cholera cultures revealed differences, while general peaks with different intensity were maintained.Conclusions: all samples of V. cholerae cultures taken for analysis aft er culture on a nutrient medium were reliably identified with a high Score. As a result of comparative analysis of protein mass spectra by the m/z value and relative intensity of peaks, no proteins characteristic only for plankton cultures or biofilms of V. cholerae were detected. The stability of the phenotypic properties of V. cholerae regardless of its form of existence and the high reliability of the MALDI-ToF mass spectrometry method for identifying both planktonic and biofilm forms of V. cholerae with the preservation of the research protocol and bacteriological culturation.

Resistance to Antiseptics and Disinfectants of Planktonic and Biofilm-Associated Forms of Corynebacterium striatum.

Disinfection and antisepsis are of primary importance in controlling nosocomial infections and outbreaks by pathogens expressing multiple resistance to antimicrobial agents (multidrug-resistant [MDR]) used in therapy. Nowadays, infections related to health services (HAIs) due to MDR and multidrug-susceptible (MDS) Corynebacterium striatum should not be underestimated, including patients using invasive medical devices. The virulence potential of C. striatum needs further investigation. Currently, susceptibility profiles of planktonic and/or sessile forms of four C. striatum strains of different pulsed-field gel electrophoresis types were examined as biocides based on the manufacturer's recommendations: 2% glutaraldehyde (GA), 2% peracetic acid (PA), 1% potassium monopersulfate (Virkon®; VK), 1% sodium hypochlorite (SH), and 70% ethyl alcohol (ET). Time-kill assays using 2% bovine serum albumin (BSA) were performed for evaluation of influence of organic matter on biocides effects. Planktonic forms expressed GA resistance at different levels. C. striatum viability was observed until 2, 4, 20, and 30 min for MDR 2369/II, MDS 1954/IV, MDR 1987/I, and MDS 1961/III strains, respectively. In contrast to GA, the biocides PA, VK24h, SH, and ET had higher effective bacterial mortality. However, storage of VK (48 hr) reduced their biocide activities. Moreover, mature biofilms were produced on abiotic substrates, including steel surfaces. Post-treatment with GA (30 min), survival of sessile forms was ≥100% than planktonic forms of all C. striatum tested strains. Independent of biocides tested, BSA increased the survival of planktonic and sessile forms (p ≤ 0.005). Present data indicated that hospital staff should be aware of dissemination and eradication of HAIs by C. striatum presenting resistance to biocides, including high-level disinfectants, such as GA.