Disclosed herein are a recombinant Streptomyces S27S5 hemagglutinin (SHA), and homologues thereof, and a fusion protein of a fluorescent protein (such as GFP and mCherry1) and SHA or a homologue thereof, which specifically bind to carbohydrates, including oligomeric sugars that terminate in L-rhamnose or D-galactose. The SHA, SHA homologues, and fusion proteins can be used to detect a variety of microorganisms or cancer or tumor antigens.