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* Sexual reproduction does not occur in bacteria. The point of departure in bacterial reproduction is always that one individual divides itself into two identical descendants. * In the bacterial world, however, there is certainly exchange of hereditary characteristics (DNA). This type of exchange is called horizontal gene transfer. * There are 3 basic ways for the exchange of DNA between bacteria: conjugation, transduction and natural transformation. Each of these has its specific impact on the species. * During conjugation, a piece of DNA is copied in one bacterium and transferred to another via a temporary connection, a conjugative pilus. In this way, for example, a particular gene that codes for resistance against antibiotics can be transmitted. * In transduction, the transfer of DNA takes place with the aid of bacteriophages. The gene that codes for the toxin produced by Vibrio cholerae is spread by transduction. * In transformation, DNA that is located outside the cell is fragmented and imported into the cell, after which, via recombination, the DNA replaces a piece of original DNA in the chromosome of the host. Transformation is responsible for, among other things, antigen variation in the pneumococcal capsule. Antigen variation helps the pneumococci to resist the immune response leading to the forming of antibodies and adequate opsonisation.

A 58-year-old man presented with hoarseness and a sore throat for the previous 3 months, which were caused by a laryngeal infection with the fungus Histoplasma capsulatum. He had been infected during a stay in Indonesia. Both his hoarseness as well as the Histoplasma antigen titres in serum responded to therapy with itraconazol. H. capsulatum is found in tropical and subtropical areas worldwide, but infections are most commonly reported from the south of the United States of America. If not asymptomatic, the disease most often presents with pulmonary symptoms. A histoplasmosis presenting as a laryngeal infection is relatively uncommon and can be mistaken for papillomatosis or carcinoma. The diagnosis can be made by microscopy and culture of the fungus; an antigen test is available in the United States.