Research in Microbiology

There are many different kinds of microorganisms in the soil, and many of them are biofilms because they can make supracellular compounds. Surface-associated microorganisms in a biofilm are encased in a hydrated extracellular polymeric substance that aids in adherence and survival. Numerous different kinds of microorganisms call the soil home. Strong interactions with and among species are made possible by biofilms; this, in turn, might increase the effectiveness with which organic compounds and poisons in soil are degraded...

Biofilms have been recognized as a serious threat to public health as it protects microbes from antimicrobials, immune defence mechanisms, chemical treatments and nutritional stress. Biofilms are also a source of concern in industries and water treatment because their presence compromises the integrity of equipment. To overcome these problems, it is necessary to identify novel anti-biofilm compounds. Products of microorganisms have been identified as promising broad-spectrum anti-biofilm agents. These natural products include biosurfactants, antimicrobial peptides, enzymes and bioactive compounds...

A circular economy requires effective re-use of finite resources, such as metals from waste electrical and electronic equipment (WEEE). Bioleaching for extraction and recovery of base metals from printed circuit boards (PCBs) before recovering precious metals has potential to increase metal circularity. However, inhibition by base metals released from the PCBs and accumulated in PCB leachates on microbial Fe2+ oxidation, a critical bioleaching sub-process for Fe3+ regeneration, can limit this approach. Here, we explore the potential of microbial immobilisation on polyurethane foam (PUF) and adaptation to cupric ions to minimise inhibition by mixed metals released from PCBs, particularly zinc, nickel, and tin, and enhancing Fe2+ oxidation rates in PCB bioleaching systems...

The sulfur oxidation kinetics of an industrial strain of Acidithiobacillus caldus (At. caldus) cultured on elemental sulfur was explored in batch experiments in the absence and presence of thiocyanate (SCN- ), a toxin inherent within cyanidation tailings wastewater. The Contois rate expression accurately described At. caldus sulfate generation (R2 > 0.93) and microbial growth (R2 > 0.87). For a culture maintained at 45°C a maximum specific growth rate (μmax ) of 0.105 h-1 , sulfate yield from biomass (Ypx ) of 4...

The opportunistic human pathogen Bacillus cereus controls the expression of key infection-promoting phenotypes using bacterial quorum sensing (QS). QS signal transduction within the species is controlled by an autoinducing peptide, PapR7 , and its cognate receptor, PlcR, indicating that the PlcR:PapR interface is a prime target for QS inhibitor development. The C-terminal region of the peptide (PapR7 ; ADLPFEF) has been successfully employed as a scaffold to develop potent QS modulators. Despite the noted importance of the C-terminal carboxylate and amide protons in crystallographic data, their role in QS activity has yet to be explored...

Sun exposure is harmful to the skin and increases the risk of skin aging and skin cancer. Here we examined the effects of daily exposure to sun radiation on the skin microbiome in order to determine whether skim microbiome bacteria can contribute to protection from solar damage. Skin swabs were collected from ten lifeguards before and after the summer to analyse the skin microbiome. The results indicates that specific skin microbiome bacteria were enriched following the seasonal sun exposure. Especially interesting were two bacterial families - Sphingomonas and Erythrobacteraceae - which may have the ability to protect against UV radiation as they produce potentially protective compounds...

One of the foremost report of apoptosis-like programmed cell death (PCD) came from Xanthomonas axonopodis pv. glycines (Xag), which displayed rapid post-exponential cell death in PCD inducing media (PIM) but not in a non-inducing media (PNIM). The current study aims to decipher for the first time, the advantages of the existence of PCD in this phytopathogenic microorganism. Analysis of RNA seq under inducing and non-inducing conditions, revealed differential expression of a number of genes related to key physiology of Xag, such as, motility, xanthan biosynthesis and export as well as virulence...

DNA integrity in bacteria is regulated by various factors that act on the DNA. trans-translation has previously been shown to be important for the survival of E. coli cells exposed to certain DNA-damaging agents. However, the mechanisms underlying this sensitivity are poorly understood. In this study, we explored the involvement of the trans-translation system in the maintenance of genome integrity using various DNA-damaging agents and mutant backgrounds. Relative viability assays showed that SsrA-defective cells were sensitive to DNA-damaging agents, such as nalidixic acid (NA), ultraviolet radiation (UV), and methyl methane sulfonate (MMS)...

Rare earth element (REE) recovery from waste streams, mine tailings or recyclable components using bioleaching is gaining traction due to the shortage and security of REE supply as well as the environmental problems that occur from processing and refining. Four heterotrophic microbial species with known phosphate solubilizing capabilities were evaluated for their ability to leach REE from a high-grade monazite when provided with either galactose, fructose or maltose. Supplying fructose resulted in the greatest amount of REE leached from the ore due to the largest amount of organic acid produced...

Extreme acidophiles thrive in acidic environments, confront a multitude of challenges and demonstrate remarkable adaptability in their metabolism to cope with the ever-changing environmental fluctuations, which encompass variations in temperature, pH levels, and the availability of electron acceptors and donors. The survival and proliferation of members within the Acidithiobacillia class rely on the deployment of transcriptional regulatory systems linked to essential physiological traits. The study of these transcriptional regulatory systems provides valuable insights into critical processes, such as energy metabolism and nutrient assimilation, and how they integrate into major genetic-metabolic circuits...

P. aeruginosa, a Gram-negative bacterium that causes severe hospital acquired infections poses threat by its ability for adaptation to various growth modes and environmental conditions and by its intrinsic resistance to antibiotics. The latter is mainly due to the outer membrane (OM) asymmetry which is maintained by the Mla pathway resulting in the retrograde transport of glycerophospholipids from the OM to the inner membrane. It comprises six Mla proteins, including MlaA, an OM lipoprotein involved in the removal of glycerophospholipids mislocalized at the outer leaflet of OM...

Biotin is an essential vitamin for all organisms. Some bacteria cannot synthesize biotin and live by acquiring biotin from the environment. Bacterial biotin transporters (BioY) are classified into three mechanistic types. The first forms the BioMNY complex with ATPase (BioM) and transmembrane protein (BioN). The second relies on a promiscuous energy coupling module. The third functions independently. One-third of bioY genes spread in bacteria cluster with bioM and bioN on the genomes, and the rest does not...

Agaricus subrufescens, also known as the "sun mushroom," has significant nutritional and medicinal value. However, its short shelf life due to the browning process results in post-harvest losses unless it's quickly dehydrated. This restricts its availability to consumers in the form of capsules. A genome sequence of A. subrufescens may lead to new cultivation alternatives or the application of gene editing strategies to delay the browning process. We assembled a chromosome-scale genome using a hybrid approach combining Illumina and Nanopore sequencing...

The Corynebacterium diphtheriae species complex comprises seven bacterial species, including Corynebacterium ulcerans, a zoonotic pathogen from multiple animal species. In this work, we characterise phenotypically and genotypically isolates belonging to two C. ulcerans lineages. Results from phylogenetic analyses, in silico DNA-DNA hybridization (DDH) and MALDI-TOF spectra differentiate lineage 2 from C. ulcerans lineage 1, which, together with their distinct transmission dynamics (human-to-human vs animal-to-human), indicates that lineage 2 is a separate Corynebacterium species, which we propose to name Corynebacterium ramonii...

Halotolerant acidophilic bioleaching microorganisms are crucial to bioleaching operations that utilize saline water. Compatible solutes play an important role in the adaptation of these microorganisms to saline environments. Acidithiobacillus ferrooxidans ATCC 23270, an iron- and sulfur-oxidizing acidophilic bacterium, synthesizes trehalose as its native compatible solute but is still sensitive to salinity. Recently, halotolerant bioleaching bacteria were found to use ectoine as their key compatible solute...

The mechanism of enhanced tigecycline MIC in Staphylococcus cohnii after in vitro tigecycline exposure was investigated. S. cohnii 11-B-312 was exposed to incremental concentrations of tigecycline (2-32 mg/L) and the mutants growing at 8, 16 and 32 mg/L were determined by AST and WGS. Copy number and relative transcription level of the tet(L) gene were determined by quantitative PCR. The fitness cost was evaluated by growth kinetics and competition assays. The results revealed that enhanced tigecycline MIC was identified in S...

Within the European research project NEMO, a bioleaching strategy was developed for efficient metal extraction from bioleach residue currently heap-leached at Sotkamo (Finland) that still contains sulphidic minerals and valuable metals (Ni, Zn, Co, Cu). The strategy of gradually increasing the solid content with 5% steps allowed the adaptation of the consortium up to 20%(w/w) solid content, with efficient metal dissolution and same dominant bacteria. Largest proportions of Sb. thermosulfidooxidans while Eh increased suggested it to be most involved in iron oxidation...

Bioleaching processes and acid mine drainage (AMD) generation are mainly driven by aerobic microbial iron(II) and inorganic sulfur/compound oxidation. Dissimilatory iron(III) reduction coupled to sulfur/compound oxidation (DIRSO) by acidophilic microorganisms has been described for anaerobic cultures, but iron reduction was observed under aerobic conditions as well. Aim of this study was to explore reaction rates and mechanisms of this process. Cell-specific iron(III) reduction rates for different Acidithiobacillus (At...

Leptospirosis, a global reemerging zoonosis caused by the spirochete Leptospira, has severe human and veterinary implications. Cell wall hydrolase (LIC_10271) with LytM (peptidase M23) and LysM domains are found to be associated with various pathogenic bacteria. These domains regulate effects on extracellular matrix and biofilm components, which promote cell wall remodeling and pathogen dissemination in the host. In this study, we present the cloning, expression, purification, and characterization of LIC_10271...

The practical significance of constructing robust industrial production strains against organic acid stress lies not only in improving fermentation efficiency but also in reducing manufacturing costs. In a previous study, we constructed an industrial Saccharomyces cerevisiae strain by modifying another PEP4-allele of a mutant that already had one PEP4-allele disrupted. This modification enhanced cellular tolerance to citric acid stress during growth. Unlike citric acid, which Saccharomyces cerevisiae can consume, tartaric acid is often added to grape must during winemaking to increase total acidity and is not metabolizable...