Total Biofilm Biomass Research Articles

Statherin-derived peptides as antifungal strategy against Candida albicans

ObjectiveThe aim of this in vitro study was to evaluate the effect of statherin and its naturally occurring peptides (DR9-2, DR9, GE-12, IT-32, GQ-19, IP-18) on Candida albicans metabolism and biofilm development. DesignAfter the killing assay, a peptide pellicle was formed on the bottom of a polystyrene plate at the IC50 of each peptide. Over the peptide pellicle, Candida albicans biofilm (48 h) was grown. The peptides antimicrobial activity after the peptides treatment was evaluated by alamarBlue, total biofilm biomass and colony forming units (CFU) counting. ResultsThe pellicle with statherin and the peptides (DR9-2, DR9, GE-12, IP-18, GQ-19) was able to reduce he viability of Candida albicans compared to the negative control. They also decreased cell proliferation by 20 % and total biomass. IT-32 showed the highest reduction in cell proliferation and biomass, which was similar to the positive control, histatin 5. ConclusionsThese results suggest that the naturally occuring peptides from statherin are able to decrease Candida albicans colonization and biofilm proliferation.

Atopobium vaginae and Prevotella bivia Are Able to Incorporate and Influence Gene Expression in a Pre-Formed Gardnerella vaginalis Biofilm.

Bacterial vaginosis (BV) is associated with a highly structured polymicrobial biofilm on the vaginal epithelium where Gardnerella species presumably play a pivotal role. Gardnerella vaginalis, Atopobium vaginae, and Prevotella bivia are vaginal pathogens detected during the early stages of incident BV. Herein, we aimed to analyze the impact of A. vaginae and P. bivia on a pre-established G. vaginalis biofilm using a novel in vitro triple-species biofilm model. Total biofilm biomass was determined by the crystal violet method. We also discriminated the bacterial populations in the biofilm and in its planktonic fraction by using PNA FISH. We further analyzed the influence of A. vaginae and P. bivia on the expression of key virulence genes of G. vaginalis by quantitative PCR. In our tested conditions, A. vaginae and P. bivia were able to incorporate into pre-established G. vaginalis biofilms but did not induce an increase in total biofilm biomass, when compared with 48-h G. vaginalis biofilms. However, they were able to significantly influence the expression of HMPREF0424_0821, a gene suggested to be associated with biofilm maintenance in G. vaginalis. This study suggests that microbial relationships between co-infecting bacteria can deeply affect the G. vaginalis biofilm, a crucial marker of BV.

Формирование биопленок природными штаммами микроорганизмов в присутствии нафталина и антрацена

In this work, the effect of low molecular polycyclic aromatic hydrocarbons (PAHs), naphthalene and anthracene, on the formation of biofilms by the strains of Acinetobacter calcoaceticus VKPM B-10353, Pseudomonas putida, and Vibrio aquamarinus VKPM B-11245 has been studied. The intensity of biofilm formation (staining with crystal violet), the number of viable cells (staining with fluorescein diacetate), as well as the metabolic activity of microbial cells included in biofilms (XTT-assay) were assessed. It was found that the studied strains are characterized by different responses to the introduction of pollutants. The V. aquamarines VKPM B-11245 strain showed mainly a protective reaction; in the presence of the studied PAHs an increase in the total bacterial biofilm biomass was observed, as well as a decrease in the number of living cells and the level of cellular metabolism. The naphthalene concentrations of 0.1% and 0.2% caused a reduction of all studied indicators. The P. putida strain is the most resistant to the action of the examined PAHs: in the presence of naphthalene, an increase in both the total biofilm biomass and cellular metabolism was observed. Anthracene enhanced cellular metabolism in this strain, which allows considering the studied P. putida strain as potentially useful for bioremediation. The A. calcoaceticus VKPM B-10353 strain was highly sensitive to naphthalene; suppression of biofilm formation was observed, as well as a decrease in cellular metabolism at all studied concentrations. However, anthracene increased biofilm biomass and enhanced the metabolism, which may indicate a potential ability of this strain to degrade this PAH. Acinetobacter calcoaceticus, Pseudomonas putida, Vibrio aquamarinus, biofilm, anthracene, naphthalene The research was financially supported by the Ministry of Science and Higher Education of the Russian Federation within the framework of state assignment no. 0852-2020-0029 in the field of scientific activity.

Non‐native Chinook salmon add nutrient subsidies and functional novelty to Patagonian streams

Abstract The impacts of non‐native species are hypothesised to be proportional to the functional distinctiveness of invaders in their invaded ecosystems. Throughout the Patagonia region of southern South America, Chinook salmon (Oncorhynchus tshawytscha) have recently established non‐native populations, and their anadromous, semelparous life cycle could be functionally unique such that marine‐derived nutrients are delivered to streams which have historically lacked such a resource linkage with the ocean. We tested the hypothesis that salmon subsidise biofilm‐associated algae in streams throughout the Aysén province of southern Chile. Using spatial and temporal variation in the presence of salmon among multiple streams and across two spawning seasons, we found strong evidence of salmon‐subsidised algae in three out of four streams examined that have spawning salmon populations. The biofilm of subsidised streams had enriched stable isotopic ratios of nitrogen and carbon, indicating that marine‐derived nutrients were incorporated by biofilms. This nutrient uptake translated into increased algal biomass and percent of total biofilm biomass composed of algae, indicating that the incorporation of marine‐derived nutrients stimulated autotrophic production of biomass. In one stream, the incorporation of marine‐derived nutrients by biofilm occurred in only one of the two studied spawning seasons. Incorporation occurred in a year with low flows of water throughout salmon spawning (4.59 m3/s) and did not occur in a year with much higher flows (41.6 m3/s), suggesting that inter‐annual variation in discharge can mediate the subsidising effect of salmon. These results indicate that Chinook salmon have bridged the historical gap between productive marine ecosystems and nutrient‐poor stream ecosystems in Patagonia. Anadromous salmon can be a significant source of nutrients in nutrient‐limited catchments, and their ongoing expansion in southern South America is likely to entail ecological impacts in stream and riparian food webs.

‘Secondary biofilms’ could cause failure of peracetic acid high-level disinfection of endoscopes

The reduced susceptibility of biofilms to disinfectants presents a challenge to the successful reprocessing of medical equipment. This study examined the effect of residual biomass remaining after previous disinfection with peracetic acid (PAA) on the tolerance of subsequent mature Pseudomonas aeruginosa biofilms to PAA. The effect of enzymatic degradation of specific components of the extracellular polymeric substance (EPS) of P. aeruginosa biofilm on the effectiveness of PAA disinfection was also evaluated. The susceptibility of biofilm grown on the biomass of PAA-killed biofilm to PAA was compared with the PAA susceptibility of biofilm grown in wells of a 24-well plate by evaluating their viability using the plate count assay. The effect of PAA on biofilm biomass was measured using crystal violet quantification of total biofilm biomass, while its effect on the polysaccharide and protein components of biofilm EPS was quantified using the phenol-sulphuric acid assay or Bradford assay, respectively. A confocal microscope was used to visualize the distribution of living and dead cells in biofilms grown on residual biofilm biomass. The presence of residual biomass from previously disinfected biofilms significantly enhanced the tolerance of subsequent biofilms. A 96-h-old 'secondary biofilm' formed on disinfected biomass survived PAA concentrations of 4000 ppm, which exceeds the concentrations used in practice for high-level disinfection. These observations indicate that, under certain circumstances, recolonization of residual EPS can cause failure of disinfection of medical equipment such as endoscopes, and emphasizes the importance of cleaning endoscopes prior to disinfection.

Antimicrobial, antibiofilm and cytotoxic effects of a colloidal nanocarrier composed by chitosan-coated iron oxide nanoparticles loaded with chlorhexidine

ObjectivesThis study evaluated the antimicrobial and antibiofilm effects of a colloidal nanocarrier for chlorhexidine (CHX) on Candida glabrata and Enterococcus faecalis, as well as tested its cytotoxic effect on murine fibroblasts. MethodsIron oxide nanoparticles (IONPs) were coated with chitosan (CS) and loaded with CHX at 31.2, 78 and 156 μg/mL. Antimicrobial effects were assessed by determining the minimum inhibitory concentration (MIC), using the broth microdilution method, and fractional inhibitory concentration index (FICI). Preformed biofilms (48 h) were treated with different concentrations of the nanocarrier (24 h) and quantified by colony-forming units (CFUs), total biomass and metabolic activity. For cytotoxicity, the viability of L929 cells was evaluated by MTT assay after 24 and 48 h of exposure to the nanocarrier. Data were submitted to ANOVA and Fisher LSD or Tukey post-hoc tests (α = 0.05). ResultsMIC and FICI results showed an indifferent interaction among the components of the nanocarrier for all strains evaluated. CHX alone and nanocarrier containing 156 μg/mL CHX did not differ from each other in reducing the number of CFUs. However, the nanocarrier containing 156 μg/mL CHX promoted the highest reductions in total biofilm biomass and metabolism, surpassing the effect of CHX alone. After 24 and 48 h of exposure, the nanocarrier reduced CHX toxicity to the L929 cell at low concentrations. ConclusionThese findings suggest that the CHX nanocarrier has potential to be used in the control of oral diseases associated with C. glabrata and E. faecalis. Clinical relevanceCHX has improved the antibiofilm effect and reduced the cytotoxicity (at low concentrations) when conjugated to CS-coated IONPs. This new colloidal formulation has potential as an alternative antimicrobial agent to pure CHX for the control of biofilm-related oral diseases, such as oral candidiasis and endodontic infections.

Natural antioxidant pterostilbene as an effective antibiofilm agent, particularly for gram-positive cocci.

Pterostilbene (PTE), a dimethylated analogue of resveratrol, mostly contained in Vitis vinifera leaves or in other plant sources is well-known for its antioxidant activity. Due to its bioavailability, low hydrophilicity and thus ability to penetrate hydrophobic biological membranes it was found to be an antimicrobial agent. These properties of PTE offer the possibility of its use in the treatment of microbial infections. The emergence of antibiotic resistance of microorganisms is often caused by their ability to form biofilm; new substances with antibiofilm activity are therefore sought. The representatives of opportunistic pathogenic gram-positive and gram-negative bacteria as well as fungi were used for the determination of minimum inhibitory concentrations (MIC50 and MIC80), minimum biofilm inhibitory concentrations (MBIC50 and MBIC80) and minimum biofilm eradication concentrations (MBEC50 and MBEC80) of PTE and commonly used antibiotics erythromycin, polymyxin B or antimycotic amphotericin B. Total biofilm biomass was investigated by crystal violet staining, and the results were confirmed using microscopic techniques. The most significant antibiofilm action was proved for gram-positive cocci, e.g., MBEC50 of PTE for all strains of Staphylococcus epidermidis tested was 25mg/L. By contrast, the antibiotic ERM did not exhibit antibiofilm activity in most cases. The permeabilization of cell membranes of gram-positive cocci biofilm by MBIC50 and MBEC50 of PTE was confirmed by LIVE/DEAD staining using spinning disc confocal microscopy. PTE significantly influenced the ability of gram-positive cocci to form biofilm and it effectively eradicated pre-formed biofilm in vitro; its potential for the treatment of biofilm-associated infections of Staphylococcus spp. or Enterococcus faecalis is thus apparent.

Grapevine extracts and their effect on selected gut-associated microbiota: In vitro study

The biological activity of polyphenol substances contained in food supplements prepared from Vitis vinifera can affect the microorganisms present in the digestive tract in terms of their representation and activity of the individual species. This study deals with resveratrol and two polyphenol-rich extracts (extract from V. vinifera canes and the commercial product Regrapex-R-forte) and their effect on selected gut microbiota (Bifidobacterium animalis subsp. lactis Bb-12, Lactobacillus acidophilus LA-5, Lactobacillus casei Lafti L-26, Citrobacter freundii DBM 3127, Escherichia coli DBM 3125). The effect of the studied agents on planktonic and biofilm growth of the microorganisms was determined as minimum inhibitory concentration (MIC80) and minimum biofilm inhibitory concentration (MBIC80), respectively. The extracts induced metabolic activity as well as total biofilm biomass production in probiotic strain L. acidophilus LA-5 while successfully inhibiting the growth of opportunistic pathogenic microorganisms C. freundii DBM 3127 and E. coli DBM 3125.

719. Cefiderocol Retains Anti-Biofilm Activity in MDR Gram-Negative Pathogens

BackgroundCefiderocol is a siderophore cephalosporin with potent antibacterial activity against a broad range of Gram-negative pathogens. Microorganisms forming biofilm, e.g., cUTI, utilize bacterial siderophores to access free iron. A siderophore antibiotic may have unique antimicrobial properties in the setting of biofilm. In this study, we compared antimicrobial activity of cefiderocol to comparator antibiotics in well-characterized multi-drug-resistant pathogens. We determined the activity of cefiderocol and comparator antibiotics in the biofilm setting.MethodsMinimum inhibitory concentrations (MICs) in Mueller–Hinton II broth (MHII) and iron-depleted cation-adjusted MHII (ID-CAMHB) were determined for cefiderocol and seven comparator antibiotics in multidrug-resistant isolates of P. aeruginosa, Burkholderia cepacia complex (Bcc), Klebsiella pneumoniae, Escherichia coli, and Acinetobacter baumannii. MBEC (minimum biofilm eradication concentration) assays were used to test cefiderocol’s activity in biofilms formed on pegs. Total biofilm biomass and viable cell number were measured.ResultsThe MIC90 of cefiderocol ranged from 0.125 μg/mL (Bcc) to 1 μg/mL (P. aeruginosa) in ID-CAMHB. MIC90 values were consistently lower for cefiderocol in all strains tested compared with other agents (ceftolozane-tazobactam, ceftazidime–avibactam, ceftazidime, pipercallin-tazobactam, imipenem, tobramycin, clarithromycin). Twenty-four hour P. aeruginosa biofilms (strains ATCC 9027, MB640, MB771, MB580A, MB730) were treated every 12 hours with 4 μg/mL of cefiderocol or comparator antibiotics. Cefiderocol treatment displayed a superior reduction in biofilm based on colony counts ( >90%; P < 0.0001 vs. untreated control) compared with comparator drugs (50 to 80% reduction). Crystal violet staining revealed a dose-dependent response of cefiderocol in the reduction of biofilm. Reduction of biofilm was not significantly altered by the growth media that was used; however, P. aeruginosa strains form more biofilm in MHII.ConclusionCefiderocol effectively reduces biofilm in multidrug-resistant strains of P. aeruginosa and is a potent inhibitor of planktonic growth across a range of Gram-negative medically important pathogens.Disclosures All authors: No reported disclosures.

Acoustically stressing biofilms formed by Pseudomonas aeruginosa

Bacterial biofilms, the complex and dynamic assemblages of bacterial cells, have shown increased tolerance to antimicrobials compared to their planktonic counterparts. Altered metabolism and micro-environments, in addition to the self-generated extracellular polymeric substances (EPS), collectively help to protect the bacteria from the effect of antimicrobials, thereby increasing the necessity for novel treatment methods that are effective against biofilms. To address this, we have investigated the effect of high intensity focused ultrasound (HIFU) in killing or dispersing biofilms. HIFU reduces the total biofilm biomass without significant cell killing. To investigate the molecular mechanism of action of HIFU, we quantified the intracellular concentrations of cyclic di-GMP, which regulates the switch between biofilm and planktonic life-styles. Biofilms grown on polymeric sheets were exposed to HIFU at 0.5 MHz frequency and the c di-GMP concentration was characterized using confocal microscopy. Changes in the c di-GMP activity localized at the acoustic focus were observed as the biomass decreased. The mechanisms promoting these changes were further investigated by examining the shape of individual bacterial colony grown on agar plates. The observed effects were compared to sham (negative control) and c di-GMP overproducing mutant (positive control).

Investigation of Gelatinase Gene Expression and Growth of &lt;i&gt;Enterococcus faecalis&lt;/i&gt; Clinical Isolates in Biofilm Models

Enterococcus faecalis is the major reason for biofilm-related infections and it also interacts with Staphylococcus aureus in biofilms. Gelatinase (gelE) enzyme is an important virulence factor of E. faecalis for biofilm formation. This study aimed to compare the biofilm producing E. faecalis isolates from urine and urinary catheters. The influence of S. aureus on the growth of E. faecalis biofilm cells was also investigated in a dual biofilm model in vitro. Another aim was to evaluate E. faecalis gelE gene expression during biofilm formation. Firstly, crystal violet staining was used to measure the total biofilm biomass of the isolates. Secondly, plate counting was performed to determine the biofilm formation ability of E. faecalis isolates and the effect of S. aureus on E. faecalis biofilm formation. Finally, the gelE expression profile of the isolates was assessed by quantitative real time-polymerase chain reaction. According to crystal violet staining and plate counting, all E. faecalis isolates were biofilm producers and the number of E. faecalis sessile cells increased in the presence of S. aureus. Among the 21 E. faecalis isolates, ten expressed high levels of the gelE gene, while eight of them had low expression profiles (p<0.05). When they grow together, S. aureus may give some advantages to E. faecalis such as increasing sessile cell growth. The expression of the gelE gene was not affected by E. faecalis biofilm formation of the isolates collected from the patients with urinary tract infections.

Effect of non-thermal plasma on AHL-dependent QS systems and biofilm formation in Pseudomonas aeruginosa: Difference between non-hospital and clinical isolates

Non-thermal plasma (NTP), generated by DC cometary discharge with a metallic grid at atmospheric pressure, was used to eradicate biofilm of Pseudomonas aeruginosa from titanium alloy Ti-6Al-4V carriers. The NTP exposure may reduce the ability of signal molecules to cause quorum sensing (QS) response in P. aeruginosa and as a result, affect the production of virulence factors including biofilm formation. Two groups of P. aeruginosa were compared, namely strains isolated from the environment (non-hospital) and clinical isolates from hospital environment. For the non-hospital strains, the inhibition of QS systems, mediated mainly by N-acyl-homoserine lactone (AHL) signals, and decrease of total biofilm biomass were observed after the NTP treatment. After 60 minutes of exposure, almost complete eradication of biofilm (54 - 98%) was achieved. Compared to that, the NTP effect on the AHL levels was more pronounced in clinical isolates of P. aeruginosa, but eradication of the biofilm was not achieved. We conclude that NTP affected the AHL-dependent QS systems (las and rhl), which does not necessarily have to result in the regulation of virulence in clinical isolates.

Seasonal changes in fatty acid composition of estuarine intertidal biofilm: Implications for western sandpiper migration

For shorebirds, long distance migration is an energy-demanding activity, and lipids (largely comprised of fatty acids) with their high energy density are an ideal fuel. Diatoms in intertidal biofilms provide a rich source of fatty acids for fuel and for critical physiological functions. We compared the composition of intertidal biofilm on mudflats at Roberts Bank, a major stopover site for shorebirds in the Fraser River estuary, between two seasons: spring, during the northward breeding migration of Western Sandpipers (Calidris mauri), and winter, when no migrating shorebirds are present. Mass fractions of fatty acids in biofilm (μg fatty acids/g sample in the upper 2 mm of biofilm-containing sediment) in April were 3–7 × higher than in winter (January and February). This difference included total saturated, monounsaturated, polyunsaturated, omega-3 (n-3), and omega-6 (n-6) fatty acids, as well as individual fatty acids such as palmitoleic acid (16:1n-7), eicosapentaenoic acid (EPA; 20:5n-3), and docosahexaenoic acid (DHA; 22:6n-3). In addition, organic content was ∼25% higher in spring compared to winter. The microphytobenthos in spring biofilm was dominated by marine-influenced diatoms (primarily from the genera Nitzschia and Navicula) which made up >50% (μg/ml) of total biofilm biomass. Higher fatty acid and organic content in biofilm during spring provide shorebirds with both energy and physiologically important fatty acids to support their migration. These findings are consistent with the ‘green wave’ hypothesis, whereby bird migration broadly coincides temporally with the availability of energy and essential nutrients. The role of diatoms as purveyors of important fatty acids to shorebirds underscores the need for new conservation policies that protect the abundance of organic and fatty acid content of intertidal biofilm at estuarine stopover sites.

Effects of Duration, Frequency, and Severity of the Non-flow Period on Stream Biofilm Metabolism

Temporary streams make up the majority of river networks in many regions around the world. Although they are known to have non-flow periods, it is uncertain in what ways the temporal components of the non-flow period affect stream ecosystems. We analyzed how duration and frequency of the non-flow period influence the biofilm metabolism of 33 Mediterranean streams in NE Iberian Peninsula. Selected streams ranged from perennial to ephemeral, and their hydrology was characterized during a period of 150 days before the sampling. Cobbles were collected from the streams, for which the total biofilm biomass (ash-free dry mass and chlorophyll-a) and metabolism (community respiration and gross primary production) were measured. Metabolic differences were observed between both permanent and temporary streams, as well as within temporary streams. Among these, the frequency of the non-flow period did not affect biofilm biomass or metabolism, but the duration did significantly decrease autotrophic biomass and gross primary production. Severity of the non-flow period (solar radiation and maximum streambed temperature) also affected gross primary production negatively. Thus, 80% of the observed gross primary production variability among all temporary streams was explained by the total duration and the severity of the non-flow period. In contrast, community respiration in the streams was not affected by the temporal components of the non-flow period. Our results highlight the effects of different temporal components of the non-flow period on autotrophic and heterotrophic processes, indicating that longer durations of the non-flow period or high severity conditions might decrease gross primary production promoting heterotrophy.

Monohexosylceramides from Rhizopus Species Isolated from Brazilian Caatinga: Chemical Characterization and Evaluation of Their Anti-Biofilm and Antibacterial Activities.

Monohexosylceramides (CMHs) are highly conserved fungal glycosphingolipids playing a role in several cellular processes such as growth, differentiation and morphological transition. In this study, we report the isolation, purification and chemical characterization of CMHs from Rhizopus stolonifer and R. microspores. Using positive ion mode ESI-MS, two major ion species were observed at m/z 750 and m/z 766, respectively. Both ion species consisted of a glucose/galactose residue attached to a ceramide moiety containing 9-methyl-4,8-sphingadienine with an amidic linkage to a hydroxylated C16:0 fatty acid. The antimicrobial activity of CMH was evaluated against Gram positive and Gram negative bacteria using the agar diffusion assay. CMH from both Rhizopus species inhibited the growth of Bacillus terrae, Micrococcus luteus (M. luteus) and Pseudomonas stutzeri (P. stutzeri) with a MIC50 of 6.25, 6.25 and 3.13 mg/mL, respectively. The bactericidal effect was detected only for M. luteus and P. stutzeri, with MBC values of 25 and 6.25 mg/mL, respectively. Furthermore, the action of CMH on the biofilm produced by methicillin-resistant Staphylococcus aureus (MRSA) was analyzed using 12.5 and 25 mg/mL of CMH from R. microsporus. Total biofilm biomass, biofilm matrix and viability of the cells that form the biofilm structure were evaluated. CMH from R. microsporus was able to inhibit the MRSA biofilm formation in all parameters tested.

Microplastics: New substrates for heterotrophic activity contribute to altering organic matter cycles in aquatic ecosystems

Heterotrophic microbes with the capability to process considerable amounts of organic matter can colonize microplastic particles (MP) in aquatic ecosystems. Weather colonization of microorganisms on MP will alter ecological niche and functioning of microbial communities remains still unanswered. Therefore, we compared the functional diversity of biofilms on microplastics when incubated in three lakes in northeastern Germany differing in trophy and limnological features. For all lakes, we compared heterotrophic activities of MP biofilms with those of microorganisms in the surrounding water by using Biolog® EcoPlates and assessed their oxygen consumption in microcosm assays with and without MP. The present study found that the total biofilm biomass was higher in the oligo-mesotrophic and dystrophic lakes than in the eutrophic lake. In all lakes, functional diversity profiles of MP biofilms consistently differed from those in the surrounding water. However, solely in the oligo-mesotrophic lake MP biofilms had a higher functional richness compared to the ambient water. These results demonstrate that the functionality and hence the ecological role of MP-associated microbial communities are context-dependent, i.e. different environments lead to substantial changes in biomass build up and heterotrophic activities of MP biofilms. We propose that MP surfaces act as new niches for aquatic microorganisms and that the constantly increasing MP pollution has the potential to globally impact carbon dynamics of pelagic environments by altering heterotrophic activities.

Mg2+ reduces biofilm quantity in Acidithiobacillus ferrooxidans through inhibiting Type IV pili formation.

Bioleaching is a promising process for 350 million tons of Jinchuan low-grade pentlandite. But high concentration of Mg2+ is harmful to bioleaching microorganisms. Interestingly, biofilm formation can improve leaching rate. Thus, it is actually necessary to investigate the effect of Mg2+ stress on Acidithiobacillus ferrooxidans biofilms formation. In this study, we found that 0.1 and 0.5 M Mg2+ stress significantly reduced the total biomass of biofilm in a dose-dependent manner. The observation results of extracellular polymeric substances and bacteria using confocal laser scanning microscopy showed that the biofilm became thinner and looser under Mg2+ stress. Whereas 0.1 and 0.5 M Mg2+ stress had no remarkable effect on the bacterial viability, the attachment rate of Acidithiobacillus ferrooxidans to pentlandite was reduced by Mg2+ stress. Furthermore, sliding motility, twitching motility and the gene expression level of pilV and pilW were inhibited under Mg2+ stress. These results suggested that Mg2+ reduced biofilm formation through inhibiting pilV and pilW gene expression, decreasing Type IV pili formation and then attenuating the ability of attachment, subduing the active expansion of biofilms mediated by twitching motility. This study provided more information about the effect of Mg2+ stress on biofilm formation and may be useful for increasing the leaching rate in low-grade pentlandit.

Effect of toothpaste containing arginine on dental plaque—A randomized controlled in situ study

ObjectivesTo evaluate the effects of 8% arginine-containing toothpaste on the dental plaque of no caries (NC) and high caries (HC) individuals in situ. Methods6 no caries (DMFT=0) and 6 high caries (DMFT≥6) individuals wearing a self-developed in situ dental plaque acquisition device were involved in a randomized double-blinded crossover study for 6 weeks: including lead-in (1 week), arginine-free (2 weeks), washout (1 week) and arginine-active (2 weeks) stages. The in situ plaque samples were collected at the endpoint of arginine-free and arginine-active stages and subjected to lactic acid production, metabolic activity, live/dead bacteria ratio and total biofilm biomass detections. ResultsThe arginine-containing dentifrice reduced lactic acid production significantly in both the NC and HC groups, while the inhibitory abilities in the HC group were stronger than that in the NC group. In addition, the arginine-containing dentifrice didn’t significantly decrease the metabolic activity, live/dead bacteria ratio and total biofilm biomass in either the NC or the HC group. ConclusionsArginine-containing toothpaste can significantly reduce the lactic acid production from the in situ plaques to a low level without changing the metabolic activity, live/dead bacteria ratio and total biofilm biomass through a critical clinical randomized double-blinded crossover study. Clinical significanceArginine is a potential ecological prevention and control agent for dental caries. Meanwhile, the in situ model is an easy and pragmatic way to evaluate oral hygiene products (clinical trial registration: ChiCTR-INR-16010226).

The effect of iron oxide nanoparticles on Bacillus subtilis biofilm, growth and viability

Abstract Bacillus subtilis is one of the key microorganisms for the industrial production of many value added products. The fermentation of this bacterium is associated with biofilm formation that results in major process and operational issues. The study of the effect of magnetic nanoparticles on the bacterial cells can immensely contribute to designing intensified bioprocess methods Present study was aimed at understanding the effect of superparamagnetic iron oxide (naked IONs) and 3-aminopropyltriethoxy silane coated IONs (IONs@APTES) on biofilm formation, growth and viability of Bacillus subtilis. Both IONs were successfully prepared and characterised by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction patterns (XRD) and vibrating sample magnetometry (VSM). IONs@APTES at 100 μg/mL were found to significantly reduce the total biofilm biomass without affecting the cell viability compared with the behavior of naked IONS, which significantly affected the viability of B. subtilis at high concentrations without any significant redution in biofilm biomass. This suggests an active role of IONs@APTES in eliminating the biofilm formation as compared to the naked IONs. This work suggests the possibility of using IONs@APTES coated bacteria for a range of applications for future industrial fermentation with Bacillus subtilis .

Effect of bacteria on the degradation ability of Pleurotus ostreatus.

White-rot fungi are efficient degraders of lignin whose extracellular enzymes have a potential to degrade organopollutants. In natural conditions these fungi enter into interactions with other organisms, which may affect their biodegradation capacity. The aim was to investigate the ability of Pleurotus ostreatus to form stable biofilms and to test the capacity of the fungus to degrade Remazol Brilliant Blue R in mixed cultures with bacteria. Bacterial counts were determined to see the behavior of the bacterium in the mixed culture with the fungus. In axenic conditions, the homogenized fungal mycelium was able to form an active biofilm which quickly degraded the dye. The addition of Pseudomonas fluorescens or Bacillus licheniformis bacteria at 106CFU·mL-1 did not affect the decolorization rate by 7-d-old fungal biofilms where the decolorization rate reached 90%. In contrast, when fragments of the fungal mycelium were used for inoculation to pre-formed biofilm of P. fluorescens, the biofilm was allowed to develop for one week's time, no decolorization of RBBR was observed and low activities of MnP and laccase were detected. The use of agar disks covered with fungal mycelium for the inoculation to pre-formed biofilm of P. fluorescens resulted in a fully developed biofilm that decolorized RBBR with similar efficiency as the pure P. ostreatus. The difference between the agar-disk- and homogenized-mycelium inoculated fungal biofilms was corroborated by the measurement of total fungal biofilm biomass that was 6-fold lower in the latter biofilm. Capability of the fungus to overcome the competition of the bacterial biofilm thus depended on the type of fungal growth centres, where intact hyphae were superior to the fragments of mycelium. A similar effect was not observed with the biofilms of B. licheniformis where the bacterial growth was less massive. The ability of P. ostreatus biofilms to resist massive bacterial stress was demonstrated.