MASMANIDOU MARIA

ZACHARIADI ISAVELLA
UNIVERSITY OF IOANNINA GREECE
BIOLOGICAL APLICATIONS AND TECHNOLOGY
AQUATIC MICROORGANISMS

WEEK: 2nd

LEFT: ¾ sediment-enrichment materials and lake water

RIGHT: ¼ sediment-enrichment materials, 2/4 sediment and lake water

On the left column, we observed that the aquatic phase got a dark green colour because of the growth of  green sulpur bacteria, such as chlorobium. Those microorganisms gain energy from light reactions and produce their cellular materials from CO2 in much the same way as plants do. However, there is one essential difference, they do not generate oxygen during photosynthesis because they do not use water as the reductant, instead, they use H₂S. We also noticed a black line on the sediment’s surface which provides the existence of black sulphur-reducing bacteria such as clostridium and desulfovibrio. They use sulphate or other partly oxidised forms of sulphur as the terminal electron acceptor, generating large amounts of H₂S by this process. The H₂S react with any iron in the sediment, producing black ferrous sulphide. This is why lake sediments are frequently black. However, some of the H₂S diffuses upwards into the water column, where it is utilised by other organisms (e.g green sulpur bacteria).

On the other hand, on the right column, we observed just a light green colour in the aquatic phase which could be a proof for the existence of Algae and Photosynthetic cyanobacteria(those microorganisms contains chlorophyll a and performs oxygenic photosynthesis).

From those indications we accepted the first hypothesis that microorganisms in the left bottle grew up faster than the right one.

WEEK: 3^rd – 4^rth

LEFT: ¾ sediment-enrichment materials and lake water

RIGHT: ¼ sediment-enrichment materials, 2/4 sediment and lake water

Our columns had no big difference between the 3rd and 4th week so we took just one photo.

The left turned purple  because of the growth of purple sulphur bacteria. These bacteria grow in anaerobic conditions, gaining their energy from light reactions but using organic acids as their carbon source for cellular synthesis. So they are termed photoheterotrophs. The organic acids that they use are the fermentation products of other anaerobic bacteria (e.g. Clostridium species). On the right one, aquatic phase turned dark green because of the green sulphur bacteria. No difference was observed in the sediment in both columns.

WEEK: 5^th

LEFT: ¾ sediment-enrichment materials and lake water

RIGHT: ¼ sediment-enrichment materials, 2/4 sediment and lake water

Both of our columns got darker and so swelled that they could not remain in an upright position. When we tried to open them, bubbles started to emerge, which is a proof of the existence and the increase in the amount of methanogens. Except the methanogens, there might have been some other obligatory anaerobic bacteria at the bottom, such as Clostridium or Desulfovibrio. Then, Desulfovibrio respire using these compounds to reduce the sulfate from the eggs. These processes quickly deplete any remaining of O₂ at the bottom of the column. Desulfovibrio release Hydrogen-Sulfide as a byproduct of said sulfate reduction. This causes a concentration gradient in the column between O₂ and H₂S (Higher O₂ at top). On the left bottle, in the aquatic anaerobic phase, grew up both green and purple photosynthetic sulphur bacteria. On the other hand,the right bottle got a purple-red colour because of the sulphur or non sulphur  photosynthetic bacteria (such as Rhodomicrobium). These bacteria use the Ethanol which produced from the clostridium as a photosynthetic reducer.

WEEK: 6^th

LEFT: ¾ sediment-enrichment materials and lake water

RIGHT: ¼ sediment-enrichment materials, 2/4 sediment and lake water

Six weeks later the column with the excess of enrichment materials (left one) got even darker in both sediment and aquatic phase. Microorganisms such as black sulphur-reducing  bacteria (in the sediment phase) and green sulphur bacteria (in the aquatic phase) continue growing up. In the right column, the aquatic phase got an orange-red colour because of the purple sulphur or non sulphur bacteria. Moreover, that colour could probably indicate cyanobacteria, who lost their chlorophylls and turned orange. No difference observed in the sediment phase in that column.

WEEK: 7^th

LEFT: ¾ sediment-enrichment materials and lake water

RIGHT: ¼ sediment-enrichment materials, 2/4 sediment and lake water

The last week, in the sediment phase, in both of our columns developed some white bacteria ( basically colourless bacteria), which use sulphate as the terminal electron acceptor, generating large amounts of H₂S by this process. Those microorganisms grow up in completely anaerobic conditions. Furthermore, both of our columns in aquatic phase turned green-orange because of the green and purple sulphur bacteria. Finally, in the left column,  grew up something like moss plants in the aquatic phase and biofilm in both columns.