Mycobacterium tuberculosis is the cause of one of the most deadly diseases of mankind, and despite the availability of effective treatments, tuberculosis (TB) remains a major public health threat. The difficult challenges in treating multiple-drugresistant (MDR) and extensively drug-resistant (XDR) TB and the importance of shortening the duration of treatment to improve patients' compliance make the discovery of new anti-TB drugs imperative (1-5). Attempts to discover new TB drugs and targets via large-scale screening against intact mycobacteria have largely been confined to synthetic compound libraries and to date have yielded only one new clinical TB drug, the diarylquinoline bedaquiline (6, 7). Although very potent, to be of maximum benefit, bedaquiline, a diarylquinoline, and nitroimidazoles (8) require new companion drugs to be used in a multidrug regimen.While the intensive search for antibiotics from soil microorganisms in the mid-20th century yielded several clinically useful TB drugs, the pathogenic nature of M. tuberculosis and its extremely slow growth rate did not allow classical agar diffusion tests and excluded M. tuberculosis from the initial target panel. The discovery of TB drugs of natural origin at that time therefore relied upon the detection of activity against nonmycobacteria in agar diffusion assays followed by bioassay-guided isolation of the active principle, again using nonmycobacteria. Activity against M. tuberculosis was only assessed once the active principle was purified.Because M. tuberculosis is uniquely susceptible to a number of antimicrobial agents, a high-throughput screening (HTS) of actinomycete extracts directly against the virulent H37Rv strain was conducted, and this campaign revealed selective anti-TB peptides produced by a genetically distinct Nonomuraea species, strain MJM5123. Here, we describe the activity profile of ecumicin, its efficacy in infected mice, the identification of its molecular target, and the elucidation of its unusual mechanism of action. MATERIALS AND METHODSHigh-throughput screening. Approximately 7,000 actinomycete cultures isolated from Korea, China, Nepal, the Philippines, Vietnam, Antarctica, and the Arctic Circle and maintained at Myongji University, South Korea, were fermented in 20-ml cultures in glucose-soybean starch (GSS) medium (rich medium), Bennett's medium (normal medium), and dextrinyeast-corn steep liquor (DYC) medium (minimal medium) (see Table S1 in the supplemental material). The mycelia and culture medium supernatants were separated and extracted with methanol and ethyl acetate, respectively. Nine extracts were thus generated from each microbial isolate.

The allyl moiety of the immunosuppressive agent FK506 is structurally unique amongst polyketides and critical for its potent biological activity. Here, we detail the biosynthetic pathway to allylmalonyl-coenzyme A (CoA), from which the FK506 allyl group is derived, based on a comprehensive chemical, biochemical and genetic interrogation of three FK506 gene clusters. A discrete polyketide synthase (PKS) with noncanonical domain architecture presumably in coordination with the fatty acid synthase pathway of the host catalyzes a multi-step enzymatic reaction to allylmalonyl-CoA via trans-2-pentenyl-acyl carrier protein. Characterization of this discrete pathway facilitated the engineered biosynthesis of novel allyl group-modified FK506 analogs, namely 36-fluoro-FK520 and 36-methyl-FK506, the latter of which exhibits improved * slim@genotech.co.kr .* joonyoon@ewha.ac.kr . 8 These authors contributed equally to this work.

ClpC1 is an emerging new target for the treatment of Mycobacterium tuberculosis infections, and several cyclic peptides (ecumicin, cyclomarin A, and lassomycin) are known to act on this target. This study identified another group of peptides, the rufomycins (RUFs), as bactericidal to M. tuberculosis through the inhibition of ClpC1 and subsequent modulation of protein degradation of intracellular proteins. Rufomycin I (RUFI) was found to be a potent and selective lead compound for both M. tuberculosis (MIC, 0.02 μM) and Mycobacterium abscessus (MIC, 0.4 μM). Spontaneously generated mutants resistant to RUFI involved seven unique single nucleotide polymorphism (SNP) mutations at three distinct codons within the N-terminal domain of clpC1 (V13, H77, and F80). RUFI also significantly decreased the proteolytic capabilities of the ClpC1/P1/P2 complex to degrade casein, while having no significant effect on the ATPase activity of ClpC1. This represents a marked difference from ecumicin, which inhibits ClpC1 proteolysis but stimulates the ATPase activity, thereby providing evidence that although these peptides share ClpC1 as a macromolecular target, their downstream effects are distinct, likely due to differences in binding.

The increasing demand for fresh-like food products and the potential health hazards of chemically preserved and processed food products have led to the advent of alternative technologies for the preservation and maintenance of the freshness of the food products. One such preservation strategy is the usage of bacteriocins or bacteriocins producing starter cultures for the preservation of the intended food matrixes. Bacteriocins are ribosomally synthesized smaller polypeptide molecules that exert antagonistic activity against closely related and unrelated group of bacteria. This review is aimed at bringing to lime light the various class of bacteriocins mainly from gram positive bacteria. The desirable characteristics of the bacteriocins which earn them a place in food preservation technology, the success story of the same in various food systems, the various challenges and the strategies employed to put them to work efficiently in various food systems has been discussed in this review. From the industrial point of view various aspects like the improvement of the producer strains, downstream processing and purification of the bacteriocins and recent trends in engineered bacteriocins has also been briefly discussed in this review.

The new tuberculosis (TB) lead ecumicin (1), a cyclic tridecapeptide, was isolated from Nonomuraea sp. MJM5123, following a high-throughput campaign for anti-TB activity. The large molecular weight of 1599 amu detected by LC-HR-MS precluded the initial inference of its molecular formula. The individual building blocks were identified by extensive NMR experiments. The resulting two possible planar structures were distinguished by LC-MS2. Determination of absolute configuration and unambiguous structural confirmation were carried out by X-ray crystallography and Marfey’s analysis.