Reduced peptidoglycan synthesis capacity impairs growth of E. coli at high salt concentration.

Gram-negative bacteria have a thin peptidoglycan layer between the cytoplasmic and outer membranes protecting the cell from osmotic challenges. Hydrolases of this structure are needed to cleave bonds to allow the newly synthesized peptidoglycan strands to be inserted by synthases. These enzymes need to be tightly regulated and their activities coordinated to prevent cell lysis. To better understand this process in Escherichia coli, we probed the genetic interactions of mrcA (encodes PBP1A) and mrcB (encodes PBP1B) with genes encoding peptidoglycan amidases and endopeptidases in envelope stress conditions. Our extensive genetic interaction network analysis revealed relatively few combinations of hydrolase gene deletions with reduced fitness in the absence of PBP1A or PBP1B, showing that none of the amidases or endopeptidases is strictly required for the functioning of one of the class A PBPs. This illustrates the robustness of the peptidoglycan growth mechanism. However, we discovered that the fitness of ∆mrcB cells is significantly reduced under high salt stress and in vitro activity assays suggest that this phenotype is caused by a reduced peptidoglycan synthesis activity of PBP1A at high salt concentration.IMPORTANCEEscherichia coli and many other bacteria have a surprisingly high number of peptidoglycan hydrolases. These enzymes function in concert with synthases to facilitate the expansion of the peptidoglycan sacculus under a range of growth and stress conditions. The synthases PBP1A and PBP1B both contribute to peptidoglycan expansion during cell division and growth. Our genetic interaction analysis revealed that these two penicillin-binding proteins (PBPs) do not need specific amidases, endopeptidases, or lytic transglycosylases for function. We show that PBP1A and PBP1B do not work equally well when cells encounter high salt stress and demonstrate that PBP1A alone cannot provide sufficient PG synthesis activity under this condition. These results show how the two class A PBPs and peptidoglycan hydrolases govern cell envelope integrity in E. coli in response to environmental challenges and particularly highlight the importance of PBP1B in maintaining cell fitness under high salt conditions.

The lipoprotein DolP affects cell separation in Escherichia coli, but not as an upstream regulator of NlpD.

Bacterial amidases are essential to split the shared envelope of adjunct daughter cells to allow cell separation. Their activity needs to be precisely controlled to prevent cell lysis. In Escherichia coli, amidase activity is controlled by three regulatory proteins NlpD, EnvC and ActS. However, recent studies linked the outer membrane lipoprotein DolP (formerly YraP) as a potential upstream regulator of NlpD. In this study we explored this link in further detail. To our surprise DolP did not modulate amidase activity in vitro and was unable to interact with NlpD in pull-down and MST (MicroScale Thermophoresis) assays. Next, we excluded the hypothesis that ΔdolP phenocopied ΔnlpD in a range of envelope stresses. However, morphological analysis of double deletion mutants of amidases (AmiA, AmiB AmiC) and amidase regulators with dolP revealed that ΔamiAΔdolP and ΔenvCΔdolP mutants display longer chain length compared to their parental strains indicating a role for DolP in cell division. Overall, we present evidence that DolP does not affect NlpD function in vitro, implying that DolP is not an upstream regulator of NlpD. However, DolP may impact daughter cell separation by interacting directly with AmiA or AmiC, or by a yet undiscovered mechanism.

Fungi as veritable tool in bioremediation of polycyclic aromatic hydrocarbons-polluted wastewater.

Polycyclic aromatic hydrocarbons of diverse forms have found application in different industries and man heavily depends on these compounds for various purposes. Thus, tonnes of thousands of polycyclic aromatic hydrocarbons are released into various water bodies yearly, resulting in pollution with great effects on aquatic lives, man, and the ecosystem at large. Hydrocarbon pollutions in wastewater are remediated by some physical and chemical methods with most of these techniques leaving a different form of harmful byproducts after the remediation. Furthermore, several species of fungi are important in the microbial bioremediation of polycyclic aromatic hydrocarbon in wastewater as they are capable of using these compounds as their source of carbon and energy in the presence of oxygenase. Fungal bioremediation is cost-effective, safer, and ecologically friendly, in addition to fungi producing polycyclic aromatic hydrocarbon degradative enzymes in high amounts, both intracellularly and extracellularly. Although optimizing the growth requirement of fungi in the field is a major challenge, current advances in the application of fungi in bioremediation address this. This review discusses in detail the technology of fungal bioremediation of polycyclic aromatic hydrocarbon in wastewater and its beneficial roles to man and the ecosystem. The benefits of remediating polycyclic aromatic hydrocarbon-polluted water with fungi and their metabolites via nanotechnology, immobilization, genomic manipulation, and other technologies to generate value-added products are highlighted in this manuscript. Information in this review will provide useful important insights to researchers and industrial professionals in the bioremediation of polycyclic aromatic hydrocarbon.

Fungi as veritable tool in current advances in nanobiotechnology.

Fungi have great prospects for synthesis, applications and developing new products in nanotechnology. In recent times, fungi use in nanotechnology is gaining more attention because of the ecological friendly state of their metabolite-mediated nanoparticles, their safety, amenability and applications in diverse fields. The diversity of the metabolites such as enzymes, polysaccharide, polypeptide, protein and other macro-molecules has made fungi a veritable tool for nanoparticles synthesis. Mechanism of fungal nano-biosynthesis from the molecular perspective has been extensively studied through various investigations on its green synthesized metal nanoparticles. Fungal nanobiotechnology has been applied in agricultural, medical and industrial sectors for goods and services improvement and delivery to mankind. Agriculturally, it has found applications in plant disease management and production of environmentally friendly, non-toxic insecticides, fungicides to enhance agricultural production in general. Medically, diagnosis and treatment of diseases, especially of microbial origin have been improved with fungal nanoparticles through more efficient drug delivery systems with great benefits to pharmaceutical industries. This review therefore explored fungal nanobiotechnology; mechanism of synthesis, characterization and potential applications in various fields of human endeavours for goods and services delivery.