Diversity phenotypic

V. Tonsvik, R. Salte, R. Sorheim, and J. Goksoyr, Comparison of phenotypic diversity and DNA heterogeneity in a population of soil bacteria, Applied and Environmental Microbiology 56 116 (1990). 

K. Bronstad, K. Dronen, L. Ovreas, and V. Torsvick, Phenotypic diversity and antibiotic resistance in soil bacterial communities, J. Ind. Microbiol. 77 253 (1996). 

Strongyloides ratti has two developmental routes in its life cycle (Fig. 5.1) and this developmental choice shows phenotypic diversity. The parasitic phase of S. ratti is a parthenogenetic female (Viney, 1994). Eggs that pass out of a host can complete the free-living phase of the life cycle by two alternative developmental routes, termed heterogonic and homogonic. In homogonic... 

Of the examples considered above, two are of phenotypic diversity in a life-history trait where the life-history trait under consideration is clearly a facultative phenomenon. That is, for developmental route in S. ratti and for arrested development, there are distinct, mutually exclusive developmental routes. Thus, diversity in these traits between different parasite lines is relatively easy to observe, as is the response to selection. Both these traits are, in part, affected by environmental conditions and so are phenotypically plastic. For S. ratti, variation in the sensitivity of this plasticity can also be seen. Although environmental sensitivity of arrested development is as yet uninvestigated, by analogy with S. ratti it is likely to vary. 

The third example considered the interaction of life-history traits (survival rates, fecundity, immunogenicity) with an environmental factor specific to parasites, namely the host immune system. Here phenotypic diversity in response to environmental conditions (host immunity) is not so readily apparent. To observe phenotypic diversity, different parasite lines need to be compared in their kinetics of infection and, to show immune-dependence, these must be complemented by control experiments in immunosuppressed hosts. Experiments seeking to select on this diversity... 

Investigating phenotypic diversity is not easy. A basic requirement is to have different lines of parasite available and in natural host species. However, being aware of the possibility of variation between individual worms would be a start. The few studies that have molecularly considered individual worms (Bianco et al., 1990 Fraser and Kennedy, 1990 Currie et al., 1998) have found variation between individual worms. Such variation may be the basis of some experimental noise . Perhaps efforts should be focused on this noise The phenotypic diversity that exists in natural, and even laboratory, populations of nematodes is maintained there by natural selection. This tells us, anthropomorphically, that such diversity matters to parasitic nematodes. It is hoped that this chapter has shown that it should also matter to us. 

Torriani, S., Zapparoli, G., and Suzzi, G. (1999). Genetic and phenotypic diversity of Saccha-romyces sensu stricto strains isolated from Amarone wine. Anton. Leeuwen. 75, 207-215. 

Stitzel JA (2008) Naturally occurring genetic variability in the nicotinic acetylcholine receptor alpha4 and alpha7 subunit genes and phenotypic diversity in humans and mice. Front Biosci 13 477 91... 

Brain cancers constitute a genetically and phenotypically diverse class of proliferative neoplasms derived from incompletely differentiated neuroglial stem cells, sometimes referred to as brain tumor stem cells (BTSCs). Early pathogenetic events... 

True HL, Linquist SL. A yeast prion provides a mechanism for genetic variation and phenotypic diversity. Nature 2000 407 477-483. 

Classical microbiologists observed that clinical isolates of M. tuberculosis displayed phenotypic diversity in laboratory culture and in animal models, but molecular genetic analysis has begun to explore this phenomenon only in the last few years. Strains responsible for human TB belong to the M. tuberculosis complex , which... 

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