Accelerating food waste conversion to renewable biogas through anaerobic digestion is crucial for sustainable energy and waste management. Hydrolysis, the initial bottleneck step, relies on microbial enzymatic activity. Our research explored the potential of microbial quorum sensing (QS) to enhance this process, a mechanism controlling extracellular enzyme production. No native QS signals were observed in food waste slurries but quorum quenching activity was widespread, suggesting an inhibitory environment for QS. A substrate pretreatment regime that fostered the proliferation of QS-capable Proteobacteria was developed. Bioaugmentation with a Pseudomonas aeruginosa strain isolated from food waste, combined with pretreatment, reduced anaerobic digestion time by 20 % and increased biogas yield. Treating P. aeruginosa with QS signal molecules increased cellulase and lipase production, providing insight into the underlying mechanism by which anaerobic digestion was enhanced. This targeted bioaugmentation approach re-engineers the microbiome, promoting QS-mediated enhancements that improve biogas production efficiency and kinetics.

Most reduced organic matter entering activated sludge systems is particulate (1–100-µm diameter) or colloidal (0.001–1-µm diameter), yet little is known about colonization of particulate organic matter by activated sludge bacteria. In this study, colonization of biopolymers (chitin, keratin, lignocellulose, lignin, and cellulose) by activated sludge bacteria was compared with colonization of glass beads in the presence and absence of regular nutrient amendment (acetate and ammonia). Scanning electron microscopy and quantitative PCR revealed chitin and cellulose were most readily colonized followed by lignin and lignocellulose, while keratin and glass beads were relatively resistant to colonization. Bacterial community profiles on particles compared to sludge confirmed that specific bacterial phylotypes preferentially colonize different biopolymers. Nitrifying bacteria proved adept at colonizing particles, achieving higher relative abundance on particles compared to bulk sludge. Denitrifying bacteria showed similar or lower relative abundance on particles compared to sludge. • Some activated sludge bacteria colonize natural biopolymers more readily than others. • Nitrifying bacteria are overrepresented in natural biopolymer biofilm communities. • Biopolymers in wastewater likely influence activated sludge community composition.

Significant safety and economic consequences accompany the premature failure of bolts, posing sustainability challenges for mining operations. Previous studies have indicated that hydrogen-induced stress corrosion cracking (HISCC), primarily influenced by microbial activities termed microbiologically influenced stress corrosion cracking (MISCC), stands as a major contributor to the premature failure of bolts in underground mines. Presently, an effective mechanism to mitigate these premature failures is lacking. In this study, multiple commercially available coatings undergo testing to assess their susceptibility and suitability in preventing HISCC and MISCC. Additionally, a purpose-developed coating is examined. The results reveal that the tested commercially available coatings either fail to prevent these types of corrosion or are unsuitable for the intricate conditions within underground mines. The laboratory results show the coating has a significant anti-acidic corrosion and anti-MISCC performance. Conversely, the coating formulated in this study successfully averts both MISCC and HISCC, proving its applicability within the complex geological environments prevalent in mines. This breakthrough offers a promising solution to mitigate premature bolt failures in complex underground geological environments. The developed coating presents a viable way forward for enhancing safety, reducing economic losses, and improving the overall sustainability of mining operations.

In the past two decades, the corrosion failures of rock reinforcement bolts in underground coal mines have been increasingly reported. Preliminary studies have shown that these failures were predominantly related to pitting and stress corrosion cracking. The analyses in affected mines indicated microbially induced corrosion (MIC) as one of the primary corrosion causes. As such, there is an urgent demand from industries to develop methods to mitigate MIC-associated failures of rock bolts in underground coal mines. This study examined epoxy coating to determine its effectiveness in preventing biofilm formation on steel surfaces and, in turn, averting MIC. The corrosion-causing bacteria were isolated and enriched from groundwater samples collected from the affected mine sites. Coated and uncoated rock bolt samples were prepared from the bolts and incubated in media in the absence and presence of the corrosion-causing bacteria. Fluorescence microscopy imaging found no evidence of bacterial biomass growth on the surface of the epoxy-coated steel surfaces after 30 days, while the non-coated surfaces were colonised by biomass. The observations suggest the potential of epoxy coating for bolt MIC prevention. Future studies to assess the applicability of epoxy coating in the underground mine environment are recommended.

Anaerobic digestion is widely used to process and recover value from food waste. Commercial food waste anaerobic digestion facilities seek improvements in process efficiency to enable higher throughput. There is limited information on the composition of microbial communities in food waste prior to digestion, limiting rational exploitation of the catalytic potential of microorganisms in pretreatment processes. To address this knowledge gap, bacterial and fungal communities in food waste samples from a commercial anaerobic digestion facility were characterised over 3 months. The abundance of 16S rRNA bacterial genes was approximately five orders of magnitude higher than the abundance of the fungal intergenic spacer (ITS) sequence, suggesting the numerical dominance of bacteria over fungi in food waste before anaerobic digestion. Evidence for the mass proliferation of bacteria in food waste during storage prior to anaerobic digestion is presented. The composition of the bacterial community shows variation over time, but lineages within the Lactobacillaceae family are consistently dominant. Nitrogen content and pH are correlated to community variation. These findings form a foundation for understanding the microbial ecology of food waste and provide opportunities to further improve the throughput of anaerobic digestion.

In the past two decades, reports of the premature failure of cable bolts used in the mining and civil industries have been increasing. Previous studies have established that failure occurs through hydrogen-induced stress corrosion cracking (HISCC), which is a type of environmentally assisted hydrogen cracking. However, to date, the cause of HISCC has been unclear. For the first time, we studied the role of microorganisms in the failure of cable bolts using components present in SCCaffected mines. Stressed coupons were prepared from the cable bolt wires and tested in groundwater with additions of sulphate-reducing bacteria, coal, clay, pyrite and lactate. It was found that hydrogen sulphide (H2S) produced by sulphate- and sulphur-reducing bacteria promoted hydrogen diffusion into the steel and, in the presence of stress, caused HISCC. This suggests that control of H2S production should be a priority for mining and civil industries to avoid premature failure of anchoring systems.

Reports on corrosion failure of cable bolts, used in mining and civil industries, have been increasing in the past two decades. The previous studies found that pitting corrosion on the surface of a cable bolt can initiate premature failure of the bolt. In this study, the role of Acidithiobacillus ferrooxidans (A. ferrooxidans) bacterium in the occurrence of pitting corrosion in cable bolts was studied. Stressed coupons, made from the wires of cable bolts, were immersed in testing bottles containing groundwater collected from an underground coal mine and a mixture of A. ferrooxidans and geomaterials. It was observed that A. ferrooxidans caused pitting corrosion on the surface of cable bolts in the near-neutral environment. The presence of geomaterials slightly affected the pH of the environment; however, it did not have any significant influence on the corrosion activity of A. ferrooxidans. This study suggests that the common bacterium A. ferrooxidans found in many underground environments can be a threat to cable bolts’ integrity by creating initiation points for other catastrophic failures such as stress corrosion cracking.

Quorum sensing is a mechanism of genetic control allowing single cell organisms to coordinate phenotypic response(s) across a local population and is often critical for ecosystem function. Although quorum sensing has been extensively studied in bacteria comparatively less is known about this mechanism in Archaea. Given the growing significance of Archaea in both natural and anthropogenic settings, it is important to delineate how widespread this phenomenon of signaling is in this domain. Employing a plasmid-based AHL biosensor in conjunction with thin layer chromatography (TLC), the present study screened a broad range of euryarchaeota isolates for potential signaling activity. Data indicated the presence of 11 new Archaeal isolates with AHL-like activity against the LuxR-based AHL biosensor, including for the first time putative AHL activity in a thermophile. The presence of multiple signals and distinct changes between growth phases were also shown via TLC. Multiple signal molecules were detected using TLC in Haloferax mucosum, Halorubrum kocurii, Natronococcus occultus and Halobacterium salinarium. The finding of multiple novel signal producers suggests the potential for quorum sensing to play an important role not only in the regulation of complex phenotypes within Archaea but the potential for cross-talk with bacterial systems.

Molecular mechanisms of aging and longevity are still mostly unknown. Mitochondria play central roles in cellular metabolism and aging. In this study, we identified three deletion mutants of mitochondrial metabolism genes (ppa2∆, dss1∆, and afg3∆) that live longer than wild-type cells. These long-lived cells harbored significantly decreased amount of mitochondrial DNA (mtDNA) and reactive oxygen species (ROS). Compared to the serpentine nature of wild-type mitochondria, a different dynamics and distribution pattern of mitochondria were observed in the mutants. Both young and old long-lived cells produced relatively low but adequate levels of ATP for cellular activities. The status of the retrograde signaling was checked by expression of CIT2 gene and found activated in long-lived mutants. The mutant cells were also profiled for their gene expression patterns, and genes that were differentially regulated were determined. All long-lived cells comprised similar pleiotropic phenotype regarding mitochondrial dynamics and functions. Thus, this study suggests that DSS1, PPA2, and AFG3 genes modulate the lifespan by altering the mitochondrial morphology and functions.

Corrosion failure is one of the serious concerns with most metal products.In the mining industry, corrosion failure of cable bolts may threaten the safety of operations and cause significant financial losses.In recent years, many cable bolt failures have been reported from several underground coal mines in Australia.Recent studies have shown that the localised environment around the cable bolts (oxygen level, groundwater, bacteria, etc.) has a significant impact on the corrosion behaviour; however, studies on the role of bacteria in the corrosion of underground support systems are still limited.This paper reports on a study of the role of a well-known bacterium in microbiologically induced corrosion of cable bolts.Acidithiobacillus ferrooxidans is found in many underground mines.The cable bolt specimens used in the study were specially designed to simulate the stress level experienced in the in situ mine condition.The specimens were analysed based on their weight loss and morphological features at the end of the study.The results indicated that the involvement of the bacteria in localised corrosion development and biofilm formation on the metal surface was a contributing factor in accelerating the corrosion of the bolt and could lead to catastrophic failure of the bolts in the long term.

Antimicrobial peptides (AMPS) and their synthetic mimics have received recent interest as new alternatives to traditional antibiotics in attempts to overcome the rise of antibiotic resistance in many microbes. AMPs are part of the natural defenses of most living organisms and they also have a unique mechanism of action against bacteria. Herein, a new series of short amphiphilic cationic peptidomimetics were synthesized by incorporating the 3'-amino-[1,1'-biphenyl]-3-carboxylic acid backbone to mimic the essential properties of natural AMPs. By altering hydrophobicity and charge, we identified the most potent analogue 25g that was active against both Gram-positive Staphylococcus aureus (MIC = 15.6 mu M) and Gram-negative Escherichia coli (MIC = 7.8 mu M) bacteria. Cytoplasmic permeability assay results revealed that 25g acts primarily by depolarization of lipids in cytoplasmic membranes. The active compounds were also investigated for their cytotoxicity to human cells, lysis of lipid bilayers using tethered bilayer lipid membranes (tBLMs) and their activity against established biofilms of S. aureus and E. coli. (C) 2017 Elsevier Masson SAS. All rights reserved.

Antimicrobial resistance in bacteria is becoming increasingly prevalent, posing a critical challenge to global health. Bacterial biofilm formation is a common resistance mechanism that reduces the effectiveness of antibiotics. Thus, the development of compounds that can disrupt bacterial biofilms is a potential strategy to combat antimicrobial resistance. We report herein the synthesis of amphipathic guanidine-embedded glyoxamide-based peptidomimetics via ring-opening reactions of N-naphthoylisatins with amines and amino acids. These compounds were investigated for their antibacterial activity by the determination of minimum inhibitory concentration (MIC) against S. aureus and E. coli. Compounds 35, 36, and 66 exhibited MIC values of 6, 8 and 10 μg mL-1 against S. aureus, respectively, while compounds 55 and 56 showed MIC values of 17 and 19 μg mL-1 against E. coli, respectively. Biofilm disruption and inhibition activities were also evaluated against various Gram-positive and Gram-negative bacteria. The most active compound 65 exhibited the greatest disruption of established biofilms by 65% in S. aureus, 61% in P. aeruginosa, and 60% in S. marcescens respectively, at 250 μM concentration, while compound 52 inhibited the formation of biofilms by 72% in S. marcescens at 250 μM. We also report here the in vitro toxicity against MRC-5 human lung fibroblast cells. Finally, the pore forming capability of the three most potent compounds were tested using tethered bilayer lipid membrane (tBLM) technology.

Biofilms are responsible for over 80% of hospital- and community-acquired infections and are highly prevalent, costly to treat, and a significant cause of morbidity and mortality. Microbiological analysis of wound infection revealed existence of polymicrobial including multiple species of bacteria (both aerobic and anaerobic), fungi, and viruses but bacteria are the principal pathogens and are responsible for early dominance, biofilm formation, and infection on wounds. For instance, reports suggest that over 50% of diabetic foot ulcerations lead to infection, and consequently lower extremity amputation. However, 85% of diabetes-related amputations are preventable if infection is treated early. Bacterial resistance to antimicrobial agents is a major factor that influences apprehends of wound healing and a potential threat to human life and economy. With the increase in bacterial resistance to antibiotics and wound regime novel strategies are essential to encounter biofilms and its associated infections.

Bacteria regulate the expression of various virulence factors and processes such as biofilm formation through a chemically-mediated communication mechanism called quorum sensing. Bacterial biofilms contribute to antimicrobial resistance as they can protect bacteria embedded in their matrix from the effects of antibiotics. Thus, developing novel quorum sensing inhibitors, which can inhibit biofilm formation, is a viable strategy to combat antimicrobial resistance. We report herein the synthesis of novel acyclic and cyclic glyoxamide derivatives via ring-opening reactions of N-acylisatins. These compounds were evaluated for their quorum sensing inhibition activity against P. aeruginosa MH602 and E. coli MT102. Compounds 20, 21 and 30 displayed the greatest quorum sensing inhibition activity against P. aeruginosa MH602, with 71.5%, 71.5%, and 74% inhibition, respectively, at 250 μM. Compounds 18, 20 and 21 exhibited the greatest QSI activity against E. coli MT102, with 71.5%, 72.1% and 73.5% quorum sensing inhibition activity, respectively. In addition, the biofilm inhibition activity was also investigated against P. aeruginosa and E. coli at 250 μM. The glyoxamide compounds 16, 18 and 19 exhibited 71.2%, 66.9%, and 66.5% inhibition of P. aeruginosa biofilms, respectively; whereas compounds 12, 20, and 22 showed the greatest inhibitory activity against E. coli biofilms with 87.9%, 90.8% and 89.5%, respectively. Finally, the determination of the in vitro toxicity against human MRC-5 lung fibroblast cells revealed that these novel glyoxamide compounds are non-toxic to human cells.

1,2-Dichloroethane (DCA) is a problematic groundwater pollutant. Factors influencing the distribution and activities of DCA-degrading bacteria are not well understood, which has hampered their application for bioremediation. Here, we used quantitative PCR to investigate the distribution of putative DCA-dehalogenating bacteria at a DCA-impacted site in Sydney (Australia). The dehalogenase genes dhlA, tceA and bvcA were detected in all groundwater samples (n = 15), while vcrA was found in 11/15 samples. The 16S rRNA gene sequences specific to the dehalogenating genera Dehalobacter, Desulfitobacterium and Dehalogenimonas were detected in 15/15, 13/15 and 13/15 samples, respectively, while Dehalococcoides sequences were found in 9/15 samples. The tceA, bvcA and vcrA genes occurred in the same samples as Dehalococcoides and Dehalobacter. Microcosm experiments confirmed the presence of bacteria capable of dechlorination under anoxic conditions. The abundance of the dhlA gene, which is found in hydrolytic DCA degraders, was positively correlated to the DCA concentration, and was unexpectedly most abundant in samples with low oxygen conditions. A dhlA-containing bacterium isolated from the site (Xanthobacter EL8) was capable of anaerobic growth on DCA under denitrifying conditions. The presence of diverse DCA-dehalogenating bacteria at this site indicates that natural attenuation or biostimulation could be valid approaches for site cleanup.

N-acetyl glucosamine, the monomer of chitin, is an abundant source of carbon and nitrogen in nature as it is the main component and breakdown product of many structural polymers. Some bacteria use N-acyl-L-homoserine lactone (AHL) mediated quorum sensing (QS) to regulate chitinase production in order to catalyze the cleavage of chitin polymers into water soluble N-acetyl-D-glucosamine (NAG) monomers. In this study, the impact of NAG on QS activities of LuxR, LasR, and CviR regulated gene expression was investigated by examining the effect of NAG on QS regulated green fluorescent protein (GFP), violacein and extracellular chitinase expression. It was discovered that NAG inhibits AHL dependent gene transcription in AHL reporter strains within the range of 50-80% reduction at low millimolar concentrations (0.25-5 mM). Evidence is presented supporting a role for both competitive inhibition at the AHL binding site of LuxR type transcriptional regulators and catabolite repression. Further, this study shows that NAG down-regulates CviR induced violacein production while simultaneously up-regulating CviR dependent extracellular enzymes, suggesting that an unknown NAG dependent regulatory component influences phenotype expression. The quorum sensing inhibiting activity of NAG also adds to the list of compounds with known quorum sensing inhibiting activities.

Bacteria communicate with one another and regulate their pathogenicity through a phenomenon known as quorum sensing (QS). When the bacterial colony reaches a threshold density, the QS system induces the production of virulence factors and the formation of biofilms, a powerful defence system against the host’s immune responses. The glucosamine monomer has been shown to disrupt the bacterial QS system by inhibiting autoinducer (AI) signalling molecules such as the acyl-homoserine lactones (AHLs). In this study, the synthesis of acetoxy-glucosamides 8, hydroxy-glucosamides 9 and 3-oxo-glucosamides 12 was performed via the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and N,N′-dicyclohexylcarbodiimide (DCC) coupling methods. All of the synthesized compounds were tested against two bacterial strains, P. aeruginosa MH602 (LasI/R-type QS) and E. coli MT102 (LuxI/R-type QS), for QS inhibitory activity. The most active compound 9b showed 79.1% QS inhibition against P. aeruginosa MH602 and 98.4% against E. coli MT102, while compound 12b showed 64.5% inhibition against P. aeruginosa MH602 and 88.1% against E. coli MT102 strain at 2mM concentration. The ability of the compounds to inhibit the production of the virulence factor pyocyanin and biofilm formation in the P. aeruginosa (PA14) strain was also examined. Finally, computational docking studies were performed with the LasR receptor protein.

Prodigiosin is a heterocyclic bacterial secondary metabolite belonging to the class of tripyrrole compounds, synthesized by various types of bacteria including Serratia species. Prodigiosin has been the subject of intense research over the last decade for its ability to induce apoptosis in several cancer cell lines. Reports suggest that prodigiosin promotes oxidative damage to double-stranded DNA (dsDNA) in the presence of copper ions and consequently leads to inhibition of cell-cycle progression and cell death. However, prodigiosin has not been previously implicated in biofilm inhibition. In this study, the link between prodigiosin and biofilm inhibition through the production of redox active metabolites is presented. Our study showed that prodigiosin (500 μM) (extracted from Serratia marcescens culture) and a prodigiosin/copper(II) (100 μM each) complex have strong RNA and dsDNA cleaving properties while they have no pronounced effect on protein. Results support a role for oxidative damage to biomolecules by H2O2 and hydroxyl radical generation. Further, it was demonstrated that reactive oxygen species scavengers significantly reduced the DNA and RNA cleaving property of prodigiosin. P. aeruginosa cell surface hydrophobicity and biofilm integrity were significantly altered due to the cleavage of nucleic acids by prodigiosin or the prodigiosin/copper(II) complex. In addition, prodigiosin also facilitated the bactericidal activity. The ability of prodigiosinto cause nucleic acid degradation offers novel opportunities to interfere with extracellular DNA dependent bacterial biofilms.

Antimicrobial peptides (AMPs) are a key component of the human immune system. Synthetic AMP mimics represent a novel strategy to counteract the increasing incidence of antimicrobial resistance. Here, we describe the synthesis of novel glyoxamide derivatives via ring-opening reactions of N-hexanoyl, N-benzoyl and N-naphthoylisatins with N,N-dimethylethane-1,2-diamine and N,N-dimethylpropane-1,3-diamine. These were converted to both the hydrochloric acid (HCl) or quaternary ammonium iodide (MeI) salts and their antibacterial activity against Staphylococcus aureus was investigated by their zone-of-inhibition and minimum inhibitory concentration (MIC). The HCl salt 22b exhibited the lowest MIC of 16 μg mL(-1), whereas the corresponding MeI salt 22c had a MIC of 39 μg mL(-1). We also investigated the in vitro toxicity of active compounds against the MRC-5 normal human lung fibroblasts and their activity against established biofilm in S. aureus.

Many microorganisms use quorum sensing to regulate several complex phenotypes, and this is accomplished by the release of a signal molecule(s) into the environment. N-acyl-homoserine lactones (AHLs) are a common class of signalling molecule utilized by a range of microorganisms (primarily Gram negative bacteria but most recently also archaea) and are often detected through the use of bacterial biosensors. Biosensors can be limited by both their specificity and sensitivity, and the aim of this study was to modify and improve current AHL detection strategies. The biosensor employed in the present study was Escherichia coli MT102 harbouring a plasmid containing a LuxR based biosensor, which produces green fluorescent protein (GFP) as a reporting mechanism. A new method of visualizing the GFP based biosensor overlaid on silica sheets for the purpose of thin-layer chromatography (TLC) is presented. This new method vastly improves sensitivity of AHL detection by a GFP biosensor than previously reported and as such represents a powerful new tool in AHL research.