Mutation of Gly-444 inactivates the S. pombe malic enzyme

A mutant malic enzyme gene, mae2⁻, was cloned from a strain of Schizosaccharomyces pombe that displayed almost no malic enzyme activity. Sequence analysis revealed only one codon-altering mutation, a guanine to adenine at nucleotide 1331, changing the glycine residue at position 444 to an aspartate residue. Gly-444 is located in Region H, previously identified as one of eight highly conserved regions in malic enzymes. We found that Gly-444 is absolutely conserved in 27 malic enzymes from various prokaryotic and eukaryotic sources, as well as in three bacterial malolactic enzymes investigated. The evolutionary conservation of Gly-444 suggests that this residue is important for enzymatic function.     

The diverse family of MmpL transporters in mycobacteria: from regulation to antimicrobial developments

Mycobacterial genomes contain large sets of loci encoding membrane proteins that belong to a family of multidrug resistance pumps designated Resistance‐Nodulation‐Cell Division (RND) permeases. Mycobacterial membrane protein Large (MmpL) transporters represent a subclass of RND transporters known to participate in the export of lipid components across the cell envelope. These surface‐exposed lipids with unusual structures play key roles in the physiology of mycobacteria and/or can act as virulence factors and immunomodulators. Defining the substrate specificity of MmpLs and their mechanisms of regulation helps understanding how mycobacteria elaborate their complex cell wall. This review describes the diversity of MmpL proteins in mycobacteria, emphasising their high abundance in a few opportunistic rapid‐growing mycobacteria. It reports the conservation of mmpL loci between Mycobacterium tuberculosis and non‐tuberculous mycobacteria, useful in predicting the role of MmpLs with unknown functions. Paradoxically, whereas MmpLs participate in drug resistance mechanisms, they represent also attractive pharmacological targets, opening the way for exciting translational applications. The most recent advances regarding structural/functional information are also provided to explain the molecular basis underlying the proton‐motive force driven lipid transport. Overall, this review emphasises the Janus‐face nature of MmpLs at the crossroads between antibiotic resistance mechanisms and exquisite vulnerability to drugs.     

What makes bacterial pathogens so sticky?

Pathogenic bacteria use a variety of cell surface adhesins to promote binding to host tissues and protein-coated biomaterials, as well as cell–cell aggregation. These cellular interactions represent the first essential step that leads to host colonization and infection. Atomic force microscopy (AFM) has greatly contributed to increase our understanding of the specific interactions at play during microbial adhesion, down to the single-molecule level. A key asset of AFM is that adhesive interactions are studied under mechanical force, which is highly relevant as surface-attached pathogens are often exposed to physical stresses in the human body. These studies have identified sophisticated binding mechanisms in adhesins, which represent promising new targets for antiadhesion therapy.     

Antimicrobial monomeric and dimeric diterpenes from the leaves of Helichrysum tenax var tenax

The hexane extract of fresh air-dried leaves of Helichrysum tenax (Asteraceae) afforded ent-beyer-15-en-19-ol (1), its 4-epimer ent-beyer-15-en-18-ol (2), 15beta,16beta-epoxide-ent-beyeran-19-ol (3), as well as (4) consisting of two units of (1) linked as a diester of malonic acid, and (5), a compound. Its constituents are (1) and (3) also linked as a diester of malonic acid. The leaves of the plant are densely covered in fine glandular trichomes. These are extremely sticky and exude a mixture of the above diterpenes. Antimicrobial tests showed that (1), in particular, was highly active (3.1 and 3.6 microg/ml) against Bacillus cereus and Staphylococcus epidermidis, respectively.     

Fungi and mycotoxins in south african maize of the 1993 crop

The most dominant fungi in South African maize for the 1993 crop wereFusarium moniliforme andFusarium subglutinans. The mycotoxins occurring with the most frequency were the fumonisins, deoxynivalenol and nivalenol. Levels of fungal infection and mycotoxins varied between white maize and yellow maize, and between the respective grades.