In the sodA sodB background, a sodCI mutation was 5-fold attenuated, which was not significantly different than the 8-fold attenuation observed in the wild type background (Table 1).
The sodB mutation conferred 15-fold attenuation in the xthA/nfo background (Table 4).
As expected, a sodB recA double mutant showed a synthetic phenotype in the mouse competition assay; deletion of sodB conferred 244-fold attenuation in the recA background compared to 4-fold in a wild type background (Table 5).
Because SodA and SodB both protect the cytoplasm from damage by superoxide, in the absence of SodB, the further loss of SodA has a dramatic effect, 300-fold attenuation, whereas in the wild-type background, loss of SodA has a negligible effect on virulence.
In contrast to this study, IDM inactivation of agrA resulted in a 3.4-fold attenuation of L. monocytogenes in Caco-2 cells, a discrepancy that might be explained by experimental conditions such as the MOI used.
Assuming a 100-fold attenuation of light over 1 mm of brain tissue (Aravanis et al., 2007), the estimated irradiance in the deepest cortical layer (1.8 mW/mm) was strong enough to induce hyperpolarizing current in neurons in vitro.
Recently, some of us have shown that mutating the E protein gene of a WNV infectious clone derived from the NY99 prototype strain to prevent glycosylation resulted in a ≈200-fold attenuation of neuroinvasiveness, but not neurovirulence, in the NIH Swiss mouse model (D.W.C. Beasley, et al., unpub. data).
As the insertion of pLSV101 into the chromosome leads to slight growth deficiencies, the intracellular growth data of a random group of more than 100 IDM mutants were collected [ 12], and an at least two-fold attenuation with respect to the average data of the control group was set as a threshold.
FRET with the PDI1A-mCherry acceptor further correlated with a two-fold attenuation in CRT-GFP's mobility as assessed by FRAP measurements in thapsigargin-treated cells, further suggesting the formation of a complex between the two proteins in the calcium depleted ER.
Due to the fact that ROS impairs the protein folding, the attenuation of oxidative stress by PPAR α activation could contribute to a more proper folding of the proteins and thus to lessened ERS.
However, the xthA/nfo mutant was 2-fold attenuated in an in vitro competition assay in LB broth (Table 3), and, therefore, the attenuation does not prove that phagocytic oxygen radicals mediate this apparent DNA damage.
