## 3 Results  
### Catabolic Diversity of Autochthonous Bacteria Inhabiting Soil Contaminated with Car Fuels  
The Biolog EcoPlate technique was applied to characterize changes in the soil community as an effect of car fuel contamination. The ability of soil bacteria to use particular groups of organic compounds is illustrated in Figure 1.  
It was found that the control and diesel-contaminated soils displayed a similar trend in the utilization of carbon sources, whereas different preferences for carbon utilization were demonstrated by microflora inhabiting the petrol-contaminated soil. In the case of bacteria present in the control and diesel treatments, carboxylic acids (CA) were the most favored source of carbon and their utilization amounted to 21%-57% and 31%-44%, respectively. Amino acids (AA) were utilized at the levels of 21%-25% and 16%-24% in the control and diesel combinations. Carbohydrates (CH) were also an \begin{table}
\begin{tabular}{c c c c} \hline
**Parameter** & **Unit** & **Unleaded 95-Octane Petrol** & **Diesel** \\ \hline Carbon atoms number & – & C\({}_{5}\)–C\({}_{12}\) & C\({}_{9}\)–C\({}_{25}\) \\ Density & g cm\({}^{-3}\) & 0.72–0.78 & 0.82–0.85 \\ PAH * content & \% & 20 & 11 \\ Sulphur content & mg kg\({}^{-1}\) & 10 & 10 \\ \hline \end{tabular}  
* PAH—Polycyclic Aromatic Hydrocarbons.  
\end{table} 
Table 1: The basic properties of petroleum substances (according to www.orlen.pl). eagerly metabolized source of carbon and their utilization oscillated in the range of 12%-21% (in the control) and 21%-28% (in the diesel-contaminated soil). The utilization of polymers (P) achieved the level of 10%-12% in the control and 11%-20% in the diesel-contaminated soil. Amines and amides (AD) were the least preferred source of carbon for the bacteria from the control and diesel-contaminated soils, with the utilization percent of 1%-5% and 1%-9%, respectively. Completely different bacterial preferences in the use of carbon sources were found in the presence of petrol contamination (Figure 1). In this case, CH were the most favourable carbon substrates (18%-59%). However, during 1 h of the experiment, bacteria in the petrol-contaminated soil started to use P with metabolic effectiveness of 51%. During the other hours (from 24 to 214 h), P were used in the range of 12%-29%. Bacteria form the petrol-contaminated environment readily metabolized CA (11%-30%) and AA (1%-18%) as well. AD seemed to be the least preferred carbon source and their utilization amounted to only 1%-3%. At 96 h, this carbon source was not used at all. The analysis of the carbon utilization patterns with the Biolog Ecoplate technique for control and contaminated soils are shown in Figure 2. The heat maps clearly reveal differences in the microbial activity between the treatments. Intensive utilization of the carbon substrates began to increase at 168-214, 120-144, and 168 h of incubation for the control, diesel, and petrol treatments, respectively. Figure 1: Total carbon source utilization response (%) tracked for control and soils contaminated with diesel and petrol for the different carbon substrate groups. Figure 2: Biolog EcoPlateTM diagram of the intensity of carbon substrate utilization for control and soil contaminated with petrol and diesel. In the control sample, the bacteria first started to metabolize L-arginine after 96 h, whilst utilization of tween 40, d-xylose, L-threonine, L-phenylalanine, \(N\)-acetyl-d-glucosamine, 4-hydroxy benzoic acid, D-malic acid, and alpha-ketobutyric acid was noted after 120 h (Figure 2). Maximal intensification of carbon substrate utilization was registered between 168 and 214 h, when bacteria from the uncontaminated soil metabolized beta-methyl-d-glucoside, glycogen, glycolyl-L-glutamic acid, i-erythritol, 2-hydroxy benzoic acid, D-cellobiose, alpha-D-lactose, D-galactonic acid gamma-lactone, D,L-alpha glycerol phosphate, tween 80, L-serine, putrescine, d-xylose, phenylethylamine, L-threonine, L-phenylalanine, alpha-cyclodextrinrin, and glucose-1-phosphate.