The microbiology of railway tracks in 3 urban locations

The microbial degradation of oil on railway tracks was studied as part of a preliminary investigation of the possible stimulation of oil biodegradation on track. Railway ballast harbours a diverse population of micro-organisms represented by species of yeast, bacteria and filamentous fungi. Highest numbers of oil-degrading organisms, around 106 g−1 of ballast, were isolated during the wetter winter months. There was some seasonal fluctuation in population composition but Pseudomonas, Rhodotorula and Cladosporium were the dominant genera. The track is arid, prone to great temperature fluctuations and appears to be nitrogen-limited in stations. High levels of iron, silicon, aluminium and tin were found in oil extracted from track. The indigenous population of micro-organisms must be finely adapted for survival in an extremely harsh environment.