VOLUM OMAGIAL - Facultatea de Ştiinţe ale Naturii şi Ştiinţe Agricole

Utilization of epifluorescence microscopy…/ Ovidius University Annals, Biology-Ecology Series 14: 127-137 (2010)
Fig 3. Aniline blue positive cells as compared with
acridine orange positive cells.
2. Cyanobacteria (natural fluorescence)
Natural fluorescence of these prokaryotic in
various natural environments (marine and sulphurous
mesothermal spring) and marine microcosms was
studied by epifluorescence microscopy (figure 4).
a b
c d
Fig 4. Natural fluorescence of gasoline-tolerant
oxygenic phototrophic microorganism from
microcosm 2 supplemented with gasoline (a);
microcosm 1 supplemented with gasoline and
nutrient (b) and microorganism isolated from
sulphurous mesothermal spring Obanul Mare
(Mangalia) (c and d).
In microcosm 1 cyanobacteria filaments are
much thinner (1.35 ± 0.27) compared with
microcosm 2 (3.87 ± 0.57) (fig.5); the significance of
this difference being under investigation.
130
Fig 5. Filaments of cyanobacteria in the M2.
3. Direct viable count
In figure 6 there are presented the results
concerning changes in average cell lengths of
bacterial populations from the two microcosms with
filtered water (0,45µm) each supplemented with yest
extract, nalidixic acid and gasoline (see Materials and
methods).
Fig 6. Average length of cells from To to T4 (after 8
hours of incubation with nalidixic acid) in the two
microcosms (M2 and control, M3)
As can be seen in Figure 6, after 8 hours of
incubations, the average length of M2 cells is about 7
µm, compared with the M3 where the cells were
maintained in high proportion in the form of cocci
(average diameter of about 2 µm). These results
argue the possibility to count viable cells, cells able
to grow, by a relatively simple method. It seems
appropriate to assume that the large increase in cell
size in bacterial populations which have been
previously selected to grow in the presence of
gasoline (microcosms 2) is due to the cells ability to
oxidize/tolerate gasoline, as compared with the
populations sampled from the control microcosms
where the proportion of gasoline tolerant bacteria is