PT  - JOURNAL ARTICLE
AU  - Shakya P. Kurukulasuriya
AU  - Mo H. Patterson
AU  - Janet E. Hill
TI  - Slipped strand mispairing in the gene encoding cell wall associated sialidase NanH3 in <em>Gardnerella</em> spp
AID  - 10.1101/2020.09.16.300947
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.09.16.300947
4099  - http://biorxiv.org/content/early/2020/09/17/2020.09.16.300947.short
4100  - http://biorxiv.org/content/early/2020/09/17/2020.09.16.300947.full
AB  - Cell wall proteins with sialidase activity are involved in carbohydrate assimilation, adhesion to mucosal surfaces, and biofilm formation. Gardnerella spp. inhabit the human vaginal microbiome and encode up to three sialidase enzymes, two of which are cell wall associated. Here we demonstrate that the gene encoding extracellular sialidase NanH3 is found almost exclusively in G. piotii and closely related Gardnerella genome sp. 3, and its presence correlates with sialidase positive phenotype in a collection of 112 Gardnerella isolates. The nanH3 gene sequence includes a homopolymeric repeat of cytosines that varies in length within cell populations, indicating that this gene is subject to slipped-strand mispairing, a mechanisms of phase variation in bacteria. Variation in the length of the homopolymer sequence results in encoding of either the full length sialidase protein or truncated peptides due to introduction of reading-frame shifts and premature stop codons. Phase variation in this extracellular, cell wall associated sialidase may be involved in immune evasion or modulation of adhesion to host epithelial cells, and formation of biofilms characteristic of the vaginal dysbiosis known as bacterial vaginosis.