Bacteria of Gluconobacter genus, especially Gluconobacter oxydans, which naturally occur on surfaces of fruits and vegetables, represent a unique group of bacteria that are broadly used as natural biological antagonists to fungi that cause spoilage and decay of fruits and vegetables. Gluconobacter oxydans is a gram-negative bacterium that belongs to the family of Acetobacteriaceae and is non-pathogenic towards man and animals. One of the elementary methods of determining the properties of a specific microorganism is monitoring its microbial growth, which is mostly presented as a growth curve. Growth of bacterium Gluconobacter oxydans was monitored by an indirect method of determinig the number of viable cells, during 72 hours at selected growth conditions, in natural substrate, apple juice, and in synthetic YPM substrate, in the presence of patulin at 28ºC. The obtained data were used to make the growth curve of Gluconobacter oxydans. The bacterium shows exceptional adjustment to extreme condiotions, like the presence of patulin, a toxic, broad-spectrum antibiotic, that causes the elongation of lag-phase of bacterial growth and absence of stationary phase of growth. The results of monitoring the bacterial growth of Gluconobacter oxydans show that the observed microorganism has better conditions for growth in synthetic substrate because of mannitol, primary carbon source.