Cleaves the terminal sialic acid (N-acetyl neuraminic acid) from carbohydrate chains in glycoproteins providing free sialic acid which can be used as carbon and energy sources. Sialidases have been suggested to be pathogenic factors in microbial infections. Facilitates cholera toxin binding to host intestinal epithelial cells by converting cell surface polysialogangliosides to GM1 monogangliosides. Hydrolysis of alpha-(2->3)-, alpha-(2->6)-, alpha-(2->8)- glycosidic linkages of terminal sialic acid residues in oligosaccharides, glycoproteins, glycolipids, colominic acid and synthetic substrates. Monomer. May be controlled by sialic acid availability and a growth-phase-dependent mechanism. Belongs to the glycosyl hydrolase 33 family.