Streptomyces meridianus sp. nov. isolated from brackish water of the Tagus estuary in Alcochete, Portugal

An isolation effort focused on sporogenous from the Tagus estuary in Alcochete, Portugal, yielded a novel actinomycetal strain, designated MTZ3.1 , which was subjected to a polyphasic taxonomic study. MTZ3.1 is characterised by morphology typical of members of the genus , with light beige coloured substrate mycelium, which does not release pigments to the culture medium and with helicoidal aerial hyphae that differentiate into spores with a light-grey colour. The phylogeny of MTZ3.1 , based on the full 16S rRNA gene sequence, indicated that its closest relatives were OF1 (98.48 %), KK1-2 (98.41 %), JCM 4342 (98.34 %), NBRC 15454 (98.34 %) and NRBC 13444 (98.34 %). Moreover, average nucleotide identity (ANI), average amino acid identity (AAI) and digital DNA-DNA hybridisation (dDDH) are below the species cutoff values (ANI 67.70 and 68.35 %, AAI 77.06 and 76.71 % and dDDH 22.10 and 21.50 % for OF1 and KK1-2 , respectively). Whole genome sequencing revealed that MTZ3.1 has a genome of 5 644 485 bp with a DNA G+C content of 71.29 mol% and 5044 coding sequences. Physiologically, MTZ3.1 is strictly aerobic, able to grow at 15-37 °C, optimally at 25 °C and between pH5 and 8 and showed high salinity tolerance, growing with 0-10 %(w/v) NaCl. Major cellular fatty acids are C , iso-C , anteiso-C and iso-C . Furthermore, it was able to utilise a variety of nitrogen and carbon sources. Antimicrobial screening indicated that MTZ3.1 has potent anti- activity. On the basis of the polyphasic data, MTZ3.1 is proposed to represent a novel species, sp. nov. (= CECT 30416 = DSM 114037 =LMG 32463 ).