Stigonematalean filamentous cyanobacteria (subsection V) represent an intriguing group of microorganisms, with exceptionally large putative gene numbers relative to other cyanobacteria, particularly Scytonema species, such as Scytonema hofmanni (PCC 7110). This raises questions regarding what these genes may encode for and how many are involved in natural product biosynthesis. Due to previously reported antimicrobial activity, a related Scytonema species (UTEX LB 1163) was chosen to investigate its anti-microbial related gene cluster diversity. The goal of this project was to sequence the genome of the cyanobacteria UTEX LB 1163, and identify any putative antibiotic-related gene clusters responsible for antibiotic biosynthesis, particularly terpenoids. Through improved culturing and DNA isolation techniques, high-quality genomic DNA was isolated from UTEX LB 1163 and the genome was sequenced, using an Illumina MiSeq sequencer. After draft genome assembly, two online genome-mining servers were utilized for the annotation of the draft genome: Antibiotics & Secondary Metabolite Analysis Shell (anti-SMASH) and the Rapid Annotations using Subsystems Technology (RAST) gene annotation servers. Using anti-SMASH annotation alone yielded sixty-three putative antibiotic-related gene clusters from the draft-genome for UTEX LB 1163, versus just two putative antibiotic gene clusters annotated for the related PCC 7110. The most abundant antibiotic gene clusters present were from the non-ribosomal peptide synthase (NRPS) family, representing 32%, while polyketide synthase (type I & II) gene clusters represented 16% of the putative antibiotic gene clusters identified. Terpenoid gene clusters represented another 16% as well, suggesting UTEX LB 1163, and some other subsection V cyanobacteria, may be capable of producing far more terpenoids than has been reported in the literature thus far. Previously, only one anti-microbial terpenoid, named scytoscalarol, was identified from UTEX LB 1163. Specifically, scytoscalarol is a 25-carbon sesterterpenoid, with a scalarane backbone that is typically identified in cytotoxic extracts from marine sponges. Scytoscalarol biosynthesis is currently under investigation. Other putative antibiotic gene clusters present in UTEX LB 1163 included bacteriocin, microviridin, hserlactone, lassopeptide, and cyanobactin antibiotic families.

Cryptic antibiotic discovery in the filamentous cyanobacterium Scytonema sp. UTEX LB 1163

253rd National Meeting (2017)

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