nanotransformation of the haemotrophic mycoplasma suis during in vitro cultivation attempts using modified cell free mycoplasma media mycoplasma suis belongs to haemotrophic mycoplasmas hms which cause infectious anaemia in a large variety of mammals to date no in vitro cultivation system for m suis or other hms has been established we hypothesised that m suis could grow in classical mycoplasma media supplemented with nutrients eg glucose ironbinding proteins which are naturally available from its host environment the porcine blood blood from experimentally m suisinfected pigs was used to inoculate either standard sp4 mycoplasma medium supplemented with ironbinding proteins transferrin haemin and haemoglobin or glucoseenriched hayflick mycoplasma medium a quantitative m suisspecific realtime pcr assay was applied to determine and quantify m suis loads weekly during 12 weekincubation the first 2 weeks after inoculation m suis loads decreased remarkably and then persisted at a stationary level over the observation time of 12 weeks in ironbinding protein or glucose supplemented media variants scanning electron microscopic analysis of liquid m suis subcultures on hayflick agar showed small denselypacked microcolonies of irregular m suis cells of reduced size 0206m indicating nanotransformation the partial 16s rdna sequence of these cultured m suis nanocells was 999 identical to m suis m suis cells derived from liquid cultures interact in vitro with porcine erythrocytes by fibrillike structures we conclude that the modified mycoplasma media used for m suis cultivation are obviously unfavourable for growth but lead to culture persistence m suis adapt to inappropriate culture conditions by alteration into nanoforms