Competitive Fitness in Coronaviruses Is Not Correlated with Size or Number of Double-Membrane Vesicles under Reduced-Temperature Growth Conditions

Al-Mulla, Hawaa M. N.; Turrell, Lauren; Smith, Nicola M.; Payne, Luke; Baliji, Surendranath; Züst, Roland; Thiel, Volker; Baker, Susan C.; Siddell, Stuart G.; Neuman, Benjamin W.

DMV size was measured in order to better understand the effects of the mutations on DMV synthesis. Altogether, 4,646 DMVs were measured at various times after infection in three continuous cell lines. Under every condition that was tested, mutant viruses formed significantly smaller DMVs than wild-type viruses (Table 2). The only revertant virus tested produced DMVs of wildtype size (Wüts18 revertant in L929 cells in Table 2 ). To control for the possibility that DMV size differences were due to variation in preparation for electron microscopy, 1,352 intracellular virions were measured from the same micrographs. No significant differences in intracellular virion size were observed (Table 2) . To-gether, this demonstrated that Brts31, Albts16, Albts22, Brts105, and Wüts18 have small DMV phenotypes at 33°C.