![]() ![]() Note the viruses (green) pass through the finer filter. (b) The size of the pores in the filter determines what is captured on the surface of the filter (animal and bacteria ) and removed from liquid passing through. ![]() Note differences in the comparative size of the membrane pores and bacteria. (a) This scanning electron micrograph shows rod-shaped bacterial cells captured on the surface of a membrane filter. Membrane filters can be used to remove cells or viruses from a solution. Filters can physically remove anything present in the solution that is larger than the virions the viruses can then be collected in the filtrate (see Figure 6.16). Virions in the liquid medium can be separated from the host cells by either centrifugation or filtration. ![]() Infected host cells (eukaryotic or prokaryotic) can be cultured and grown, and then the growth medium can be harvested as a source of virus. Unlike bacteria, many of which can be grown on an artificial nutrient medium, viruses require a living host cell for replication. Today, porcelain filters have been replaced with membrane filters and other devices used to isolate and identify viruses. Compare in vivo and in vitro techniques used to cultivate virusesĪt the beginning of this chapter, we described how porcelain Chamberland filters with pores small enough to allow viruses to pass through were used to discover TMV.Describe the cultivation of viruses and specimen collection and handling.Discuss why viruses were originally described as filterable agents. ![]()
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January 2023
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