The performance and improvement of an aerosol mass spectrometer for the real time analysis of bacteria is described. The instrument can select the particles that emit fluorescence when irradiated with 266 nm laser light, for further investigation by mass spectrometry. The interference of soot particles onto the preselection is investigated and a minor interference of soot is determined. The mass spectra produced by the aerosol MALDI mass spectrometer have the high resolution and cover a mass range up to 80 kDalton. The capability of the aerosol mass spectrometer to produce good quality spectra of bacteria particles is shown with a mass spectrum of Erwinia herbicola.