The research was conducted to determine the number and species composition of microorganisms isolated from the soils collected in the vicinity of seven largest transport nodes and roundabouts in Krakow. Moreover, the investigations aimed at verifying the differences in the occurrence and biodiversity of the researched microorganism population between four calendar seasons of the year. The soil samples were collected 4 times during the period from November 2013 to August 2014 and then analysed using serial dilutions method. A great microorganism biodiversity was found in the analysed samples. Microorganisms were the most numerous in the autumn-winter period. The most numerous isolated group were vegetative bacteria and ammonifiers. Filamentous fungi were less numerous, which may have been caused by the neutral or slightly alkaline soil pH. Presence of dormant bacteria forms may result from unfavourable environmental conditions caused by a toxic effect of the substances from road transport. Less numerously isolated were actinomycetes and Azotobacter bacteria, regarded as bioindicators of soil fertility. It was found, that the differences in the numbers of the analysed microorganisms over the year are statistically significant for the vegetative and ammonifying bacteria, phytopathogenic fungi and actinomycetes. No significant differences in the microorganism number were stated ...
