Proceedings Volume 2010 (format .pdf) - SimpBTH

Fig 2. Average length of cells from T 0 to T 4 (during 8 hours of incubation with nalidixicacid and yeast extract) in the three microcosmsAs one can see in figure 3 at the start of the incubation period (in the presence ofnalidixic acid and yeast extract) there is a difference in the average length of cellsin M2 (sea water and gasoline) or M1 (sea water, gasoline and ammonium acetate)as compared with the control (sea water). The average cell length in control (M3) islower than in M2 or M1, probably because of the lack of extra nutrients. In M3(control) one can see an almost constant length of cells during incubation (1.79±0.17) whereas in M2 there was a sudden increase in cell length at time T 2 (4 hoursincubation). However, after 8 hours of incubations, the average length of cells inmicrocosms is about 4µm (M1) and 7 µm (M2), compared with the M3 where thecells were maintained in high proportion in the form of cocci (average length ofabout 1.7 µm). So far, it is not clear why the cells from M2 reach a greater length(7 µm) as compared with those from M1 (4µm), a result that deserves furtherattention to understand its signification.The average cell length was obtained by measuring the length of all cells in the 10-40 microscopic fields, including cells which didn’t really increase their lengthduring incubation period.In order to count the number and to show the increase in cell length of those cellswhich really doubled (or more) their cellular size during incubation period (8hours) all the measurements done on each microcosms at each sampling time wereordered in Excel, from the smallest to the greatest cell length. Using theperformance of Excel, at this stage of the work was counted only those cells whichreally increase as compared with the average length at the beginning of theincubation period (fig. 3). The length of these selected cells was taken into accountto calculate the average length of only growing cells (see fig. 4).208