bacteria and examined microscopically. minor changes, however cannot always be detected by microscopy. the ability of bacteria to infect live animals or plants. even if manipulated bacteria are shown in vitro to be able to infect host cells, their ability to sustain an infection in a live organism cannot be taken for granted. the expression levels of other genes. this can be assayed in several ways, notably northern blot and rt-pcr. the expression levels of the entire genome can be assayed by microarray. many type iii transcription factors and regulatory networks were discovered using these methods. the growth and fitness of bacteria. inhibitors of the t3ss a few compounds have been discovered that inhibit the t3ss in gram-negative bacteria, including the guadinomines which are naturally produced by streptomyces species. monoclonal antibodies have been developed that inhibit the t3ss too. aurodox, an antibiotic capable of inhibiting the translation of t3ss proteins has been shown to able to prevent t3ss effectors in vitro and in animal models type iii signal peptide prediction tools effectivet3