Bacterioplankton

Under the terms of bacterioplankton and Virioplankton is defined as the smallest components of the plankton. The bacterioplankton is formed by all the free-floating in the water bacteria and archaea, so it contains the smallest aquatic organisms. All present in the aquatic viruses are called Virioplankton.

Classification by size

The size spectrum of the bacterioplankton is approximately between 0.1 and 5 microns. It thus distributed among the size categories of Femtoplanktons ( organisms in size from 0.02 to 0.2 microns ), the picoplankton ( 0,2 - 2,0 microns ) and nanoplankton ( 2.0 to 20 microns ). By far the largest part of the bacterioplankton part of the picoplankton.

The size category of Femtoplanktons is largely identical to the Virioplankton. It contains plankton components of a size that are often visible only with special staining techniques or electron microscopy. It is almost exclusively formed by occurring in the water column viruses infect mainly bacteriophages, ie viruses that aquatic bacteria. However, viruses that infect algae and protozoa, these include. It is estimated that about ten times more viruses occur as bacteria in the water. Even in the drinking water there are about 105 to 106 phages per milliliter. From numerous samples it has been calculated that in the oceans occurs a number of about 1031 viruses. To illustrate this enormous number, the following thought experiment may serve: If you were to line up all these viruses, there would be despite their submicroscopic size a chain of about 400,000 light years in length. ( Our galaxy has a diameter of about 100,000 light-years. )

A large group of aquatic viruses form Cyanophagen. These viruses infect cyanobacteria. Cyanophagen have great importance for the control masse proliferating cyanobacteria in summer ( " algae bloom "). Most of these cyanobacteria are resistant by filamentous growth and toxin formation against grazing by rotifers and crustaceans. However Cyanophagen act a proliferation effectively counter (kill -the- winner- hypothesis). Accordingly, a highlight of the Cyanophagenzahl in water is observed shortly after the peak of the Cyanobakterienentwicklung. It is interesting that Cyanophagen often possess genes for processes of bacterial photosynthesis. Infected cyanobacteria thus lose control of their photosystem and are forced to provide energy and components for phage amplification.

Importance in the ecosystem

Virio and bacterioplankton have great importance for the metabolism in the waters. Photosynthetic bacteria (eg, purple, green and cyanobacteria and phototrophic Chlorobien and archaea ) form in addition to algae with its primary production of aquatic food webs basis. They are the food source for protozoa and rotifers, which are in turn eaten by larger organisms (eg crustaceans ). Much of the material conversion but does not occur in higher trophic levels, but by interactions of viruses and bacteria with each other ( " microbial loop" ). About 50 percent of all planktonic prokaryotes contain at least one functional phage genome, ie are infected by a virus. If the bacteria are killed by viruses, this requires immediate release nutrients. In addition, the bacterioplankton is relevant, that is involved in the degradation of pollutants into waters of self- purification processes. The importance of Virio and bacterioplankton and their interactions are studied by the Limnomikrobiologie or marine microbiology.