Molecular Microbiology

Fungal cell walls represent the frontline contact with the host and play a prime role in pathogenesis. While the roles of the cell wall polymers like chitin and branched β-glucan are well understood in vegetative and pathogenic development, that of the most prominent galactose-containing polymers galactosaminogalactan and fungal-type galactomannan is unknown in plant pathogenic fungi. Mining the genome of the maize pathogen Colletotrichum graminicola identified the single-copy key galactose metabolism genes UGE1 and UGM1, encoding a UDP-glucose-4-epimerase and UDP-galactopyranose mutase, respectively...

Aspergillus flavus is an agriculturally significant micro-fungus having potential to contaminate food and feed crops with toxic secondary metabolites such as aflatoxin (AF) and cyclopiazonic acid (CPA). Research has shown A. flavus strains can overcome heterokaryon incompatibility and undergo meiotic recombination as teleomorphs. Although evidence of recombination in the AF gene cluster has been reported, the impacts of recombination on genotype and metabolomic phenotype in a single generation are lacking. In previous studies, we paired an aflatoxigenic MAT1-1 A...

Plasmodium sporozoites are the highly motile and invasive forms of the malaria parasite transmitted by mosquitoes. Sporozoites form within oocysts at the midgut wall of the mosquito, egress from oocysts and enter salivary glands prior to transmission. The GPI-anchored major surface protein, the circumsporozoite protein (CSP) is important for Plasmodium sporozoite formation, egress, migration and invasion. To visualize CSP, we previously generated full-length versions of CSP internally tagged with the green fluorescent protein, GFP...

The site-specific recombination pathway of bacteriophage λ encompasses isoenergetic but highly directional and tightly regulated integrative and excisive reactions that integrate and excise the vial chromosome into and out of the bacterial chromosome. The reactions require 240 bp of phage DNA and 21 bp of bacterial DNA comprising 16 protein binding sites that are differentially used in each pathway by the phage-encoded Int and Xis proteins and the host-encoded integration host factor and factor for inversion stimulation proteins...

Microorganisms play a central role in biotechnology and it is key that we develop strategies to engineer and optimize their functionality. To this end, most efforts have focused on introducing genetic manipulations in microorganisms which are then grown either in monoculture or in mixed-species consortia. An alternative strategy to optimize microbial processes is to rationally engineer the environment in which microbes grow. The microbial environment is multidimensional, including factors such as temperature, pH, salinity, nutrient composition, etc...

The sole unifying feature of the incredibly diverse Archaea is their isoprenoid-based ether-linked lipid membranes. Unique lipid membrane composition, including an abundance of membrane-spanning tetraether lipids, impart resistance to extreme conditions. Many questions remain, however, regarding the synthesis and modification of tetraether lipids and how dynamic changes to archaeal lipid membrane composition support hyperthermophily. Tetraether membranes, termed glycerol dibiphytanyl glycerol tetraethers (GDGTs), are generated by tetraether synthase (Tes) by joining the tails of two bilayer lipids known as archaeol...

In the human pathogen Staphylococcus aureus, branched-chain fatty acids (BCFAs) are the most abundant fatty acids in membrane phospholipids. Strains deficient for BCFAs synthesis experience auxotrophy in laboratory culture and attenuated virulence during infection. Furthermore, the membrane of S. aureus is among the main targets for antibiotic therapy. Therefore, determining the mechanisms involved in BCFAs synthesis is critical to manage S. aureus infections. Here, we report that the overexpression of SAUSA300_2542 (annotated to encode an acyl-CoA synthetase) restores BCFAs synthesis in strains lacking the canonical biosynthetic pathway catalyzed by the branched-chain α-keto acid dehydrogenase (BKDH) complex...

No abstract text is available yet for this article.

The diarrheal disease cholera is caused by the versatile and responsive bacterium Vibrio cholerae, which is capable of adapting to environmental changes. Among others, the alternative sigma factor RpoS activates response pathways, including regulation of motility- and chemotaxis-related genes under nutrient-poor conditions in V. cholerae. Although RpoS has been well characterised, links between RpoS and other regulatory networks remain unclear. In this study, we identified the ArcAB two-component system to control rpoS transcription and RpoS protein stability in V...

Pathogenic Rhodococcus equi release the virulence-associated protein A (VapA) within macrophage phagosomes. VapA permeabilizes phagosome and lysosome membranes and reduces acidification of both compartments. Using biophysical techniques, we found that VapA interacts with model membranes in four steps: (i) binding, change of mechanical properties, (ii) formation of specific membrane domains, (iii) permeabilization within the domains, and (iv) pH-specific transformation of domains. Biosensor data revealed that VapA binds to membranes in one step at pH 6...

The nosocomial bacterium Acinetobacter baumannii is protected from antibiotic treatment by acquiring antibiotic resistances and by forming biofilms. Cell attachment, one of the first steps in biofilm formation, is normally induced by environmental metabolites. We hypothesized that vanillic acid (VA), the oxidized form of vanillin and a widely available metabolite, may play a role in A. baumannii cell attachment. We first discovered that A. baumannii actively breaks down VA through the evolutionarily conserved vanABKP genes...

Mycoplasma belong to the genus Mollicutes and are notable for their small genome sizes (500-1300 kb) and limited biosynthetic capabilities. They exhibit pathogenicity by invading various cell types to survive as intracellular pathogens. Adhesion is a crucial prerequisite for successful invasion and is orchestrated by the interplay between mycoplasma surface adhesins and specific receptors on the host cell membrane. Invasion relies heavily on clathrin- and caveolae-mediated internalization, accompanied by multiple activated kinases, cytoskeletal rearrangement, and a myriad of morphological alterations, such as membrane invagination, nuclear hypertrophy and aggregation, cytoplasmic edema, and vacuolization...

Small multidrug resistance transporters efflux toxic compounds from bacteria and are a minimal system to understand multidrug transport. Most previous studies have focused on EmrE, the model SMR from Escherichia coli, finding that EmrE has a broader substrate profile than previously thought and that EmrE may perform multiple types of transport, resulting in substrate-dependent resistance or susceptibility. Here, we performed a broad screen to identify potential substrates of three other SMRs: PAsmr from Pseudomonas aeruginosa; FTsmr from Francisella tularensis; and SAsmr from Staphylococcus aureus...

No abstract text is available yet for this article.

Invasive candidiasis caused by non-albicans species has been on the rise, with Candida glabrata emerging as the second most common etiological agent. Candida glabrata possesses an intrinsically lower susceptibility to azoles and an alarming propensity to rapidly develop high-level azole resistance during treatment. In this study, we have developed an efficient piggyBac (PB) transposon-mediated mutagenesis system in C. glabrata to conduct genome-wide genetic screens and applied it to profile genes that contribute to azole resistance...

Endoplasmic reticulum (ER) plays a pivotal role in the regulation of stress responses in multiple eukaryotic cells. However, little is known about the effector mechanisms that regulate stress responses in ER of the malaria parasite. Herein, we aimed to identify the importance of a transmembrane protein 33 (TMEM33)-domain-containing protein in life cycle of the rodent malaria parasite Plasmodium berghei. TMEM33 is an ER membrane-resident protein that is involved in regulating stress responses in various eukaryotic cells...

Activation and function of virulence functions of bacterial pathogens are highly dynamic in time and space, and can show considerable heterogeneity between individual cells in pathogen populations. To investigate the complex events in host-pathogen interactions, single cell analyses are required. Fluorescent proteins (FPs) are excellent tools to follow the fate of individual bacterial cells during infection, and can also be deployed to use the pathogen as a sensor for its specific environment in host cells or host organisms...

Apicomplexan parasites are aetiological agents of numerous diseases in humans and livestock. Functional genomics studies in these parasites enable the identification of biological mechanisms and protein functions that can be targeted for therapeutic intervention. Recent improvements in forward genetics and whole-genome screens utilising CRISPR/Cas technology have revolutionised the functional analysis of genes during Apicomplexan infection of host cells. Here, we highlight key discoveries from CRISPR/Cas9 screens in Apicomplexa or their infected host cells and discuss remaining challenges to maximise this technology that may help answer fundamental questions about parasite-host interactions...

No abstract text is available yet for this article.

Microbial cells must continually adapt their physiology in the face of changing environmental conditions. Archaea living in extreme conditions, such as saturated salinity, represent important examples of such resilience. The model salt-loving organism Haloferax volcanii exhibits remarkable plasticity in its morphology, biofilm formation, and motility in response to variations in nutrients and cell density. However, the mechanisms regulating these lifestyle transitions remain unclear. In prior research, we showed that the transcriptional regulator, TrmB, maintains the rod shape in the related species Halobacterium salinarum by activating the expression of enzyme-coding genes in the gluconeogenesis metabolic pathway...