Streptomyces lunalinharesii spores contain chitin on the outer sheath

Chitin from Streptomyces lunalinharesii spores, detected on its outermost surface layer, was isolated and characterized by chemical and spectroscopic methods, transmission electron microscopy and flow cytometry analysis. Gold–chitinase- and gold–lectin ( Lycopersicum esculentum agglutinin, LEA)-conjugated labels were used in microscopy experiments, whereas a fluorescence–lectin (LEA) conjugate was used in flow cytometry analysis. Chitin isolation consisted of several steps of hot alkali and nitrous acid treatment, and the final material was obtained in the colloidal form. The infrared and the ¹³C CP/MAS NMR spectra of Streptomyces sp. colloidal chitin and colloidal chitin obtained from commercial crab shell chitin were very similar. Incubation of the spores with gold-labeled lectin, or gold-labeled recombinant chitinase, showed the presence of gold particles around the spore surface, indicating the specific binding of the lectin or the recombinant chitinase with the chitin present on the outermost surface. Flow cytometry analysis, using the fluorescence–lectin conjugate, confirmed these results. According to scanning electron microscopy, S. lunalinharesii presented spore surface ornamentation belonging to the spiny group. This is the first detailed characterization of chitin on the spore's outermost layer from a Streptomyces species.