Oomycetes are eukaryotic fungus-like microorganisms that are well known for the pathogenic species contained within the group causing enormous damage to both plants and animals. Pathogenic oomycetes have huge economic impact in both wild and cultured ecosystems which has driven the focus of oomycete research mainly toward pathogenic species. Hence, the environmental studies of oomycetes, especially animal pathogenic oomycetes have been undermined. Animal pathogenic oomycetes, such as Saprolegnia species are destructive pathogens to many aquatic organisms and are found in most parts of the world. A number of Saprolegnia species e.g. S. delica, S. hypogyna, S. diclina were isolated from aquatic insects and amphipods and it was demonstrated that isolates of Saprolegnia from insects as well as known fish pathogens were highly pathogenic to eggs of Atlantic salmon (Salmo salar), nymphs of stoneflies (Perla bipunctata) and embryos of the African clawed frog (Xenopus laevis). Detailed light and scanning electron microscopy of the infected hosts revealed that Saprolegnia species form appressorium-like structures on selective hosts. It was found that a subset of papain like C1 Cysteine proteases in Saprolegnia parasitica were highly up regulated during infection of different hosts. Environmental sampling from different environments i.e. UK, the Falkland Islands and Antarctic Peninsula illustrated the diversity of oomycetes with as many as seven novel species being identified and characterised that belong to the genus Saprolegnia, Leptolegnia and Pythium in addition to many known species of oomycetes belonging to the families Saprolegniaceae and Pythiaceae. These results suggest that Saprolegnia spp. are capable of infecting multiple hosts, which may give them an advantage during seasonal variation in their natural environments. The results also suggest a model for infection of aquatic animals whereby both biochemical and mechanical force may be required to enter animal host cells. Furthermore, this thesis identifies and enlists novel as well as known oomycetes from different environments.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:606489 |
| Date | January 2014 |
| Creators | Sarowar, Mohammad Nasif |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=211246 |
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