Presence of Capsules on “Non-Capsulated” Microorganisms. ∗

Abstract

That capsules may be rather widely distributed throughout the bacterial field has been frequently suggested. Streptococci with capsules were reported by Tavel and Krumbein 1 (cf. the “strepto-cocque auréolé” of LeRoy de Barres and Weinberg 2 ) and Hiss 3 convinced himself that many if not all strains of Streptococcus pyogenes are capsulated. Boni 4 claimed to have demonstrated the presence of these structures on many different types of organisms. However his method of covering the smears (before staining) with egg albumin and glycerine hardly provided conditions in which artefacts could be excluded, and this fact has thrown considerable doubt on the inference he drew. Still, the statement is often encountered in the literature that many, if not all, varieties of bacteria may be cap-sulated; a statement which is correctly described as a guess. Hun-toon is generally known to have thought that he had demonstrated capsules on several varieties of “noncapsulated” bacteria. His only published statement, however, appears to be the following, written in connection with the description of the capsular stain with which his name is connected 5 : “This method has been tried on streptococci, staphylococci, members of the Gram negative group and many flagellate bacilli and has in no instance shown a capsule on these organisms though a similar structure may be demonstrated on all by means of a special technic which will be the subject of a subsequent report.”

By the technique described in the previous communication we have examined smears from agar cultures of the following “noncapsulated” organisms and have found them to be surrounded by a definite structure, limited by a membranous periphery selectively stained pink, which is similar to the capsule-like structure demonstrable about Diplococcus pneumoniae by the same staining method.