The Gram-negative permeability barrier: tipping the balance of the in and the out.

Gram-negative bacteria are intrinsically resistant to many antibiotics, due in large part to the permeability barrier formed by their cell envelope. The complex and synergistic interplay of the two Gram-negative membranes and active efflux prevents the accumulation of a diverse range of compounds that are effective against Gram-positive bacteria. A lack of detailed information on how components of the cell envelope contribute to this has been identified as a key barrier to the rational development of new antibiotics with efficacy against Gram-negative species.

AadT, a new weapon in fight against antibiotics.

Genes encoding a novel multidrug efflux pump, AadT, from the Drug:H antiporter 2 family, were discovered in multidrug resistance plasmids. Here, we profiled the antimicrobial resistance potential, and examined the distribution of these genes. homologs were found in many and other Gram-negative species and were typically adjacent to novel variants of ), which encodes a major tripartite efflux pump in .

Breaching the Barrier: Genome-Wide Investigation into the Role of a Primary Amine in Promoting E. coli Outer-Membrane Passage and Growth Inhibition by Ampicillin.

Gram-negative bacteria are problematic for antibiotic development due to the low permeability of their cell envelopes. To rationally design new antibiotics capable of breaching this barrier, more information is required about the specific components of the cell envelope that prevent the passage of compounds with different physiochemical properties. Ampicillin and benzylpenicillin are β-lactam antibiotics with identical chemical structures except for a clever synthetic addition of a primary amine group in ampicillin, which promotes its accumulation in Gram-negatives.

Increasing the PACE of characterising novel transporters by functional genomics.

Since the late 1990's the genome sequences for thousands of species of bacteria have been released into public databases. The release of each new genome sequence typically revealed the presence of tens to hundreds of uncharacterised genes encoding putative membrane proteins and more recently, microbial metagenomics has revealed countless more of these uncharacterised genes. Given the importance of small molecule efflux in bacteria, it is likely that a significant proportion of these genes encode for novel efflux proteins, but the elucidation of these functions is challenging.

Physiological Functions of Bacterial "Multidrug" Efflux Pumps.

Bacterial multidrug efflux pumps have come to prominence in human and veterinary pathogenesis because they help bacteria protect themselves against the antimicrobials used to overcome their infections. However, it is increasingly realized that many, probably most, such pumps have physiological roles that are distinct from protection of bacteria against antimicrobials administered by humans. Here we undertake a broad survey of the proteins involved, allied to detailed examples of their evolution, energetics, structures, chemical recognition, and molecular mechanisms, together with the experimental strategies that enable rapid and economical progress in understanding their true physiological roles.

NPC1-mTORC1 Signaling Couples Cholesterol Sensing to Organelle Homeostasis and Is a Targetable Pathway in Niemann-Pick Type C.

Lysosomes promote cellular homeostasis through macromolecular hydrolysis within their lumen and metabolic signaling by the mTORC1 kinase on their limiting membranes. Both hydrolytic and signaling functions require precise regulation of lysosomal cholesterol content. In Niemann-Pick type C (NPC), loss of the cholesterol exporter, NPC1, causes cholesterol accumulation within lysosomes, leading to mTORC1 hyperactivation, disrupted mitochondrial function, and neurodegeneration.

Tunability of DNA Polymerase Stability during Eukaryotic DNA Replication.

Structural and biochemical studies have revealed the basic principles of how the replisome duplicates genomic DNA, but little is known about its dynamics during DNA replication. We reconstitute the 34 proteins needed to form the S. cerevisiae replisome and show how changing local concentrations of the key DNA polymerases tunes the ability of the complex to efficiently recycle these proteins or to dynamically exchange them.

A randomized control trial of group counseling in a naltrexone treatment program.

This study evaluated the additional effectiveness of a 12-week manualized group counseling program over a structured naltrexone treatment program. The randomized controlled trial, the first of its kind in Australia, was conducted at Turning Point Alcohol and Drug Centre, Melbourne, Australia. Ninety-seven participants received a 50 mg dose of naltrexone daily and were randomized to either the experimental (n = 52) or control (n = 45) conditions.

Naltrexone maintenance for heroin dependence: uptake, attrition and retention.

With naltrexone registered only recently in Australia in 1999, it is important to examine the rate of uptake of naltrexone treatment, early attrition and retention rates during treatment, in order to inform the way naltrexone is used in Australian practice. Of 317 people screened for the study, 97 participants were recruited post-withdrawal from opiates and were inducted to naltrexone after a period of at least 5 days of abstinence. While in treatment, participants received a 50-mg dose of naltrexone daily, with daily dispensing for the first 7 days, and weekly dispensing for the following 11 weeks.