Abstract

Two unknown Gram-stain-positive, catalase- and oxidasenegative, non-motile, and coccus-shaped bacteria, designated MN-17T and MN-09, were isolated from yaks faeces (Bos grunniens) in the Qinghai-Tibet Plateau of China. 16S rRNA gene sequence-based comparative analyses revealed that the two strains were grouped within the genus Vagococcus, displaying the highest similarity with Vagococcus xieshaowenii CGMCC 1.16436T (98.6%) and Vagococcus elongatus CCUG 51432T (96.4%). Both strains grew optimally at 37°C and pH 7.0 in the presence of 0.5% (w/v) NaCl. The complete genome of MN-17T comprises 2,085 putative genes with a total of 2,190,262 bp and an average G + C content of 36.7 mol%. The major fatty acids were C16:0 (31.2%), C14:0 (28.5%), and C18:1ω9c (13.0%); the predominant respiratory quinone was MK-7 (68.8%); the peptidoglycan type was A4α(L-Lys-DAsp); and the major polar lipid was diphosphatidylglycerol. Together, these supported the affiliation of strain MN-17T to the genus Vagococcus. In silico DNA-DNA hybridization and the average nucleotide identity values between MN-17T and all recognized species in the genus were 21.6–26.1% and 70.7–83.0%, respectively. MN-17T produced acid from D-cellobiose, D-fructose, glycerol, D-glucose, N-acetyl-glucosamine, gentiobiose, D-mannose, D-maltose, D-ribose, Dsaccharose, salicin, D-trehalose, and D-xylose. These results distinguished MN-17T and MN-09 from closely related species in Vagococcus. Thus, we propose that strains MN-17T and MN-09 represent a novel species in the genus Vagococcus, with the name Vagococcus zengguangii sp. The type strain is MN-17T (= CGMCC 1.16726T = GDMCC 1.1589T = JCM 33478T).

• Keywords: COVID-19;bacterial vector vaccine;heterologous vaccine;trained immunity;viral vector vaccine