Natural products from Myxococcales and Bacillales & Description of a new myxobacterial taxon

Abstract

With the advent of new pathogens and upsurge in the number of antibiotic resistant microbes, concerted efforts need to be made by pharmaceutical, biotechnological and academic communities to pace up the antibiotic discovery programs and combat these deadly pathogens to ensure progress in health sector. Natural products continue to be a plenteous source of new chemical entities with distinct biological activities in extended screening programs. Microbe derived natural products and analogues have found applications in wide range of fields from pharmaceuticals to agriculture. The present thesis mainly focused on natural products isolation and characterization from myxobacteria and Paenibacillus larvae and identification and description of a novel myxobacterial taxon, Aggregicoccus edoensis. In order to find new compounds, 50 myxobacterial strains from our in house myxobacterial collection and two genotypes (ERIC I and ERIC II) of Paenibacillus larvae were cultivated and screened by biological assays, HPLC and HPLC-HRESIMS analysis. The compounds recognized as new metabolites were subsequently purified and characterized followed by structure elucidation. Pyrronazols and phenazine derivatives purified from Nannocystis pusilla, strain Ari7 give an insight of yet unexhausted metabolic diversity of microbes, specifically, of myxobacteria. Furthermore, description of paenilarvins from P. larvae is the first report of purification of secondary metabolites from this deadly honey bee pathogen. It is known that novel microbial taxa have a huge potency to detect new secondary metabolites. Hence, with an aim to identify novel myxobacterial taxa amongst the group of myxobacteria screened for natural products, their 16S rRNA genes were analyzed and compared to representative strains of the validly published taxa to determine their position in the myxobacterial phylogeny. One strain which delineated from other myxobacterial strains during phylogenetic studies was compared to the type strains of closely related genera for proteomics, fatty acid content and antibiotic resistance and described as a representative of a new genus, Aggregicoccus edoensis. Comprehensive screening of this novel taxon can possibly grant access to new myxobacterial metabolites.