Correction: Alhasso et al. Development of a Nanoemulgel for the Topical Application of Mupirocin. Pharmaceutics 2023, 15, 2387.

Simon P [...].

Bacillus-based probiotic cleansers reduce the formation of dry biofilms on common hospital surfaces.

In the absence of liquid suspension, dry biofilms can form upon hard surfaces within a hospital environment, representing a healthcare-associated infection risk. Probiotic cleansers using generally recognized as safe organisms, such as those of the Bacillus genus, represent a potential strategy for the reduction of dry biofilm bioburden. The mechanisms of action and efficacy of these cleaners are, however, poorly understood. To address this, a preventative dry biofilm assay was developed using steel, melamine, and ceramic surfaces to assess the ability of a commercially available Bacillus spp. based probiotic cleanser to reduce the surface bioburden of Escherichia coli and Staphylococcus aureus. Via this assay, phosphate-buffered saline controls were able to generate dry biofilms within 7 days of incubation, with the application of the probiotic cleanser able to prevent >97.7% of dry biofilm formation across both pathogen analogs and surface types. Further to this, surfaces treated with the probiotic mixture alone also showed a reduction in dry biofilm across both pathogen and surface types. Confocal laser scanning microscopy imaging indicated that the probiotic bacteria were able to germinate and colonize surfaces, likely forming a protective layer upon these hard surfaces.

The evolution of alkaliphilic biofilm communities in response to extreme alkaline pH values.

Extremes of pH present a challenge to microbial life and our understanding of survival strategies for microbial consortia, particularly at high pH, remains limited. The utilization of extracellular polymeric substances within complex biofilms allows micro-organisms to obtain a greater level of control over their immediate environment. This manipulation of the immediate environment may confer a survival advantage in adverse conditions to biofilms. Within the present study alkaliphilic biofilms were created at pH 11.0, 12.0, or 13.0 from an existing alkaliphilic community. In each pH system, the biofilm matrix provided pH buffering, with the internal pH being 1.0-1.5 pH units lower than the aqueous environment. Increasing pH resulted in a reduced removal of substrate and standing biomass associated with the biofilm. At the highest pH investigated (pH 13.0), the biofilms matrix contained a greater degree of eDNA and the microbial community was dominated by Dietzia sp. and Anaerobranca sp.

Hydrogenotrophic Methanogenesis Under Alkaline Conditions.

A cement-based geological disposal facility (GDF) is one potential option for the disposal of intermediate level radioactive wastes. The presence of both organic and metallic materials within a GDF provides the opportunity for both acetoclastic and hydrogenotrophic methanogenesis. However, for these processes to proceed, they need to adapt to the alkaline environment generated by the cementitious materials employed in backfilling and construction. Within the present study, a range of alkaline and neutral pH sediments were investigated to determine the upper pH limit and the preferred route of methane generation. In all cases, the acetoclastic route did not proceed above pH 9.0, and the hydrogenotrophic route dominated methane generation under alkaline conditions. In some alkaline sediments, acetate metabolism was coupled to hydrogenotrophic methanogenesis via syntrophic acetate oxidation, which was confirmed through inhibition studies employing fluoromethane. The absence of acetoclastic methanogenesis at alkaline pH values (>pH 9.0) is attributed to the dominance of the acetate anion over the uncharged, undissociated acid. Under these conditions, acetoclastic methanogens require an active transport system to access their substrate. The data indicate that hydrogenotrophic methanogenesis is the dominant methanogenic pathway under alkaline conditions (>pH 9.0).

Genomic Insights Into A Novel, Alkalitolerant Nitrogen Fixing Bacteria, Azonexus sp. Strain ZS02.

Alkaline environments represent a significant challenge to the growth of micro-organisms. Despite this, there are a number of alkaline environments which contain active microbial communities. Here we describe the genome of a diazotrophic, alkalitolerant strain of Azonexus, which was isolated from a microcosm seeded with hyperalkaline soils resulting from lime depositions. The isolate has a genome size 3.60 Mb with 3431 protein coding genes. The proteome indicated the presence of genes associated with the cycling of nitrogen, in particular the fixation of atmospheric nitrogen. Although closely related to Azonexus hydrophilus strain d8-1 by both 16S (97.9%) and in silico gDNA (84.1%) relatedness, the isolate demonstrates a pH tolerance above that reported for this strain. The proteome contained genes for the complete Na+/H+ antiporter (subunits A to G) for cytoplasmic pH regulation; this may account for the phenotypic characteristics of this strain which exhibited optimal growth conditions of pH 9 and 30°C.

Sustained Bauxite Residue Rehabilitation with Gypsum and Organic Matter 16 years after Initial Treatment.

Bauxite residue is a high volume byproduct of alumina manufacture which is commonly disposed of in purpose-built bauxite residue disposal areas (BRDAs). Natural waters interacting with bauxite residue are characteristically highly alkaline, and have elevated concentrations of Na, Al, and other trace metals. Rehabilitation of BRDAs is therefore often costly and resource/infrastructure intensive. Data is presented from three neighboring plots of bauxite residue that was deposited 20 years ago. One plot was amended 16 years ago with process sand, organic matter, gypsum, and seeded (fully treated), another plot was amended 16 years ago with process sand, organic matter, and seeded (partially treated), and a third plot was left untreated. These surface treatments lower alkalinity and salinity, and thus produce a substrate more suitable for biological colonisation from seeding. The reduction of pH leads to much lower Al, V, and As mobility in the actively treated residue and the beneficial effects of treatment extend passively 20-30 cm below the depth of the original amendment. These positive rehabilitation effects are maintained after 2 decades due to the presence of an active and resilient biological community. This treatment may provide a lower cost solution to BRDA end of use closure plans and orphaned BRDA rehabilitation.

Whole-Genome Sequence of the Anaerobic Isosaccharinic Acid Degrading Isolate, Macellibacteroides fermentans Strain HH-ZS.

The ability of micro-organisms to degrade isosaccharinic acids (ISAs) while tolerating hyperalkaline conditions is pivotal to our understanding of the biogeochemistry associated within these environs, but also in scenarios pertaining to the cementitious disposal of radioactive wastes. An alkalitolerant, ISA degrading micro-organism was isolated from the hyperalkaline soils resulting from lime depositions. Here, we report the first whole-genome sequence, ISA degradation profile and carbohydrate preoteome of a Macellibacteroides fermentans strain HH-ZS, 4.08 Mb in size, coding 3,241 proteins, 64 tRNA, and 1 rRNA.

Draft Whole-Genome Sequence of the Alkaliphilic Alishewanella aestuarii Strain HH-ZS, Isolated from Historical Lime Kiln Waste-Contaminated Soil.

Here, we present the whole-genome sequence of an environmental Gram-negative Alishewanella aestuarii strain (HH-ZS), isolated from the hyperalkaline contaminated soil of a historical lime kiln in Buxton, United Kingdom.

Microbial Community Evolution Is Significantly Impacted by the Use of Calcium Isosaccharinic Acid as an Analogue for the Products of Alkaline Cellulose Degradation.

Diasteriomeric isosaccharinic acid (ISA) is an important consideration within safety assessments for the disposal of the United Kingdoms' nuclear waste legacy, where it may potentially influence radionuclide migration. Since the intrusion of micro-organisms may occur within a disposal concept, the impact of ISA may be impacted by microbial metabolism. Within the present study we have established two polymicrobial consortia derived from a hyperalkaline soil. Here, α-ISA and a diatereomeric mix of ISAs' were used as a sole carbon source, reflecting two common substrates appearing within the literature. The metabolism of ISA within these two consortia was similar, where ISA degradation resulted in the acetogenesis and hydrogenotrophic methanogenesis. The chemical data obtained confirm that the diastereomeric nature of ISA is likely to have no impact on its metabolism within alkaline environments. High throughput sequencing of the original soil showed a diverse community which, in the presence of ISA allowed for the dominance the Clostridiales associated taxa with Clostridium clariflavum prevalent. Further taxonomic investigation at the genus level showed that there was in fact a significant difference (p = 0.004) between the two community profiles. Our study demonstrates that the selection of carbon substrate is likely to have a significant impact on microbial community composition estimations, which may have implications with respect to a safety assessment of an ILW-GDF.

Role of an organic carbon-rich soil and Fe(III) reduction in reducing the toxicity and environmental mobility of chromium(VI) at a COPR disposal site.

Cr(VI) is an important contaminant found at sites where chromium ore processing residue (COPR) is deposited. No low cost treatment exists for Cr(VI) leaching from such sites. This study investigated the mechanism of interaction of alkaline Cr(VI)-containing leachate with an Fe(II)-containing organic matter rich soil beneath the waste. The soil currently contains 0.8% Cr, shown to be present as Cr(III)(OH)3 in EXAFS analysis. Lab tests confirmed that the reaction of Cr(VI) in site leachate with Fe(II) present in the soil was stoichiometrically correct for a reductive mechanism of Cr accumulation. However, the amount of Fe(II) present in the soil was insufficient to maintain long term Cr(VI) reduction at historic infiltration rates. The soil contains a population of bacteria dominated by a Mangroviflexus-like species, that is closely related to known fermentative bacteria, and a community capable of sustaining Fe(III) reduction in alkaline culture. It is therefore likely that in situ fermentative metabolism supported by organic matter in the soil produces more labile organic substrates (lactate was detected) that support microbial Fe(III) reduction. It is therefore suggested that addition of solid phase organic matter to soils adjacent to COPR may reduce the long term spread of Cr(VI) in the environment.

Anoxic Biodegradation of Isosaccharinic Acids at Alkaline pH by Natural Microbial Communities.

One design concept for the long-term management of the UK's intermediate level radioactive wastes (ILW) is disposal to a cementitious geological disposal facility (GDF). Under the alkaline (10.013.0) anoxic conditions expected within a GDF, cellulosic wastes will undergo chemical hydrolysis. The resulting cellulose degradation products (CDP) are dominated by α- and ß-isosaccharinic acids (ISA), which present an organic carbon source that may enable subsequent microbial colonisation of a GDF. Microcosms established from neutral, near-surface sediments demonstrated complete ISA degradation under methanogenic conditions up to pH 10.0. Degradation decreased as pH increased, with ß-ISA fermentation more heavily influenced than α-ISA. This reduction in degradation rate was accompanied by a shift in microbial population away from organisms related to Clostridium sporosphaeroides to a more diverse Clostridial community. The increase in pH to 10.0 saw an increase in detection of Alcaligenes aquatilis and a dominance of hydrogenotrophic methanogens within the Archaeal population. Methane was generated up to pH 10.0 with acetate accumulation at higher pH values reflecting a reduced detection of acetoclastic methanogens. An increase in pH to 11.0 resulted in the accumulation of ISA, the absence of methanogenesis and the loss of biomass from the system. This study is the first to demonstrate methanogenesis from ISA by near surface microbial communities not previously exposed to these compounds up to and including pH 10.0.

Draft Genome Sequences of Pseudomonas aeruginosa Strain PS3 and Citrobacter freundii Strain SA79 Obtained from a Wound Dressing-Associated Biofilm.

Two isolates, one from the genus Pseudomonas and the second from Citrobacter, were isolated from a wound dressing-associated biofilm. Following whole-genome sequencing, the two isolates presented genes encoding for resistance to antibiotics and those involved in exopolysaccharide production.

Draft Genome Sequence of the Biofilm-Forming Stenotrophomonas maltophilia Strain 53.

A clinical strain of Stenotrophomonas maltophilia (designated strain 53) was obtained, and a whole-genome sequence was generated. The subsequent draft whole-genome sequence demonstrated the presence of a number of genes encoding for proteins involved in resistance to a number of antimicrobial therapies.

Evidence of the generation of isosaccharinic acids and their subsequent degradation by local microbial consortia within hyper-alkaline contaminated soils, with relevance to intermediate level radioactive waste disposal.

The contamination of surface environments with hydroxide rich wastes leads to the formation of high pH (>11.0) soil profiles. One such site is a legacy lime works at Harpur Hill, Derbyshire where soil profile indicated in-situ pH values up to pH 12. Soil and porewater profiles around the site indicated clear evidence of the presence of the α and ß stereoisomers of isosaccharinic acid (ISA) resulting from the anoxic, alkaline degradation of cellulosic material. ISAs are of particular interest with regards to the disposal of cellulosic materials contained within the intermediate level waste (ILW) inventory of the United Kingdom, where they may influence radionuclide mobility via complexation events occurring within a geological disposal facility (GDF) concept. The mixing of uncontaminated soils with the alkaline leachate of the site resulted in ISA generation, where the rate of generation in-situ is likely to be dependent upon the prevailing temperature of the soil. Microbial consortia present in the uncontaminated soil were capable of surviving conditions imposed by the alkaline leachate and demonstrated the ability to utilise ISAs as a carbon source. Leachate-contaminated soil was sub-cultured in a cellulose degradation product driven microcosm operating at pH 11, the consortia present were capable of the degradation of ISAs and the generation of methane from the resultant H2/CO2 produced from fermentation processes. Following microbial community analysis, fermentation processes appear to be predominated by Clostridia from the genus Alkaliphilus sp, with methanogenesis being attributed to Methanobacterium and Methanomassiliicoccus sp. The study is the first to identify the generation of ISA within an anthropogenic environment and advocates the notion that microbial activity within an ILW-GDF is likely to influence the impact of ISAs upon radionuclide migration.

Draft Genome Sequence of Alkaliphilic Exiguobacterium sp. Strain HUD, Isolated from a Polymicrobial Consortia.

An alkaliphilic microorganism from the genus Exiguobacterium, Exiguobacterium sp. strain HUD was isolated from a fermentative, methanogenic polymicrobial microcosm operating at pH 10. The draft genome shows the presence of genes encoding for the metabolism of a range of carbohydrates under both aerobic and anaerobic conditions.

Biodegradation of the alkaline cellulose degradation products generated during radioactive waste disposal.

The anoxic, alkaline hydrolysis of cellulosic materials generates a range of cellulose degradation products (CDP) including α and ß forms of isosaccharinic acid (ISA) and is expected to occur in radioactive waste disposal sites receiving intermediate level radioactive wastes. The generation of ISA's is of particular relevance to the disposal of these wastes since they are able to form complexes with radioelements such as Pu enhancing their migration. This study demonstrates that microbial communities present in near-surface anoxic sediments are able to degrade CDP including both forms of ISA via iron reduction, sulphate reduction and methanogenesis, without any prior exposure to these substrates. No significant difference (n = 6, p = 0.118) in α and ß ISA degradation rates were seen under either iron reducing, sulphate reducing or methanogenic conditions, giving an overall mean degradation rate of 4.7 × 10(-2) hr(-1) (SE ± 2.9 × 10(-3)). These results suggest that a radioactive waste disposal site is likely to be colonised by organisms able to degrade CDP and associated ISA's during the construction and operational phase of the facility.