Evaluation of anti-biofilm activity of acidic amino acids and synergy with ciprofloxacin on Staphylococcus aureus biofilms

Acidic amino acids, aspartic acid (Asp) and glutamic acid (Glu) can enhance the solubility of many poorly soluble drugs including ciprofloxacin (Cip). One of the mechanisms of resistance within a biofilm is retardation of drug diffusion due to poor penetration across the matrix. To overcome this challenge, this work set to investigate novel counter ion approach with acidic amino acids, which we hypothesised will disrupt the biofilm matrix as well as simultaneously improve drug effectiveness. The anti-biofilm activity of D-Asp and D-Glu was studied on Staphylococcus aureus biofilms. Synergistic effect of combining D-amino acids with Cip was also investigated as a strategy to overcome anti-microbial resistance in these biofilms. Interestingly at equimolar combinations, D-Asp and D-Glu were able to significantly disperse (at 20 mM and 40 mM) established biofilms and inhibit (at 10 mM, 20 mM and 40 mM) new biofilm formation in the absence of an antibiotic. Moreover, our study confirmed L-amino acids also exhibit anti-biofilm activity. The synergistic effect of acidic amino acids with Cip was observed at lower concentration ranges (<40 mM amino acids and <90.54 µM, respectively), which resulted in 96.89% (inhibition) and 97.60% (dispersal) reduction in CFU with exposure to 40 mM amino acids. Confocal imaging indicated that the amino acids disrupt the honeycomb-like extracellular DNA (eDNA) meshwork whilst also preventing its formation

Regulation of antibiotic production in Actinobacteria: new perspectives from the post-genomic era

The antimicrobial activity of many of their natural products has brought prominence to the Streptomycetaceae, a family of Gram-positive bacteria that inhabit both soil and aquatic sediments. In the natural environment, antimicrobial compounds are likely to limit the growth of competitors, thereby offering a selective advantage to the producer, in particular when nutrients become limited and the developmental programme leading to spores commences. The study of the control of this secondary metabolism continues to offer insights into its integration with a complex lifecycle that takes multiple cues from the environment and primary metabolism. Such information can then be harnessed to devise laboratory screening conditions to discover compounds with new or improved clinical value. Here we provide an update of the review we published in NPR in 2011. Besides providing the essential background, we focus on recent developments in our understanding of the underlying regulatory networks, ecological triggers of natural product biosynthesis, contributions from comparative genomics and approaches to awaken the biosynthesis of otherwise silent or cryptic natural products. In addition, we highlight recent discoveries on the control of antibiotic production in other Actinobacteria, which have gained considerable attention since the start of the genomics revolution. New technologies that have the potential to produce a step change in our understanding of the regulation of secondary metabolism are also described

Methods for the genetic manipulation of Nonomuraea sp. ATCC 39727.

Nonomuraea sp. ATCC 39727 belongs to the Streptosporangiaceae family of filamentous actinomycetes. This microorganism produces the teicoplanin-like glycopeptide A40926, which is the starting material for the synthesis of the second-generation glycopeptide dalbavancin. Notwithstanding the strain's pharmaceutical relevance, the lack or poor efficiency of genetic tools to manipulate Nonomuraea sp. ATCC 39727 has hampered strain and product improvement. Here we report the development of gene transfer systems based on protoplast transformation and intergeneric conjugation from Escherichia coli. Efficiency of transformation and conjugation, followed by site specific or homologous recombination with the Nonomuraea sp. genome, were determined using the integrative plasmid pSET152 (5.7 kb), and the Supercos1 derivative cosmid A40DY (30 kb). To our knowledge, this is the first report of the transformation of protoplasts of Nonomuraea sp. ATCC 39727, even though the improved procedure for intergeneric conjugation makes it the method of choice for introducing large segments of DNA into Nonomuraea sp. ATCC 39727