Epistatic interactions between gltA1 and the citT mutation in this evolved genetic background prevented a massive fitness defect that would have almost certainly led to the rapid extinction of any newly evolved Cit+ cells before this rudimentary trait could be refined to the advantageous Cit++ phenotype by further mutations.
The rudimentary Cit+ trait enabled very limited utilization of some of the abundant citrate present in the growth medium.
The first gltA mutation, which increases CS activity by disrupting NADH-inhibition of this enzyme, is beneficial for growth on the acetate and contributed to preserving the rudimentary Cit+ trait from extinction when it first evolved.
The presence of the citT mutation, which is sufficient for the rudimentary Cit+ trait on its own, slightly improves the growth dynamics and final cell density in this genetic background that includes gltA1 and other evolved alleles.
Subsequently, this rudimentary Cit+ trait was refined to a stronger phenotype, Cit++, when cells that were capable of fully exploiting citrate during each 24 hr growth cycle evolved, coincident with a large increase in cell density in this LTEE population (Blount et al., 2008).
These negative mutations accumulate until the traits they are responsible for become rudimentary or even lost.
As the default network has been shown to exhibit intrinsic, spontaneous activity, and suggested to support a baseline level of brain activity, the current results hint at possible relationships between the activity of default network regions (and the rudimentary psychological processes they may subserve) and measurable personality traits and behavioral tendencies.
Although our understanding of the neural mechanisms that sustain personality remains too rudimentary to specify how these volume changes are related, one plausible hypothesis is that personality traits represent the net output of a balance of competing processes.
Trials are often rudimentary.
These now seem rudimentary.
The furniture is very rudimentary.
