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A Regulatory Trade-Off as a Source of Strain Variation in the Species Escherichia coli. Thea King, 2004.There are few existing indications that strain variation in prokaryotic gene regulation is common or has evolutionary advantage . In this study, we report on isolates of Escherichia coli with distinct ratios of sigma factors (RpoD,  D,
or
70
and RpoS or
S)
that affect transcription initiated by RNA polymerase . Both
laboratory E . coli K-12 lineages and nondomesticated isolates
exhibit strain-specific endogenous levels of RpoS protein . We
demonstrate that variation in genome usage underpins intraspecific
variability in transcription patterns, resistance to external
stresses, and the choice of beneficial mutations under nutrient
limitation . Most unexpectedly, RpoS also controlled strain variation
with respect to the metabolic capability of bacteria with more than a
dozen carbon sources . Strains with higher
S
levels were more resistant to external stress but metabolized fewer
substrates and poorly competed for low concentrations of nutrients .
On the other hand, strains with lower
S
levels had broader nutritional capabilities and better competitive
ability with low nutrient concentrations but low resistance to
external stress . In other words, RpoS influenced both r and
K strategist functions of bacteria simultaneously . The
evolutionary principle driving strain variation is proposed to be a
conceptually novel trade-off that we term SPANC (for
"self-preservation and nutritional competence") . The availability of
multiple SPANC settings potentially broadens the niche occupied by a
species consisting of individuals with narrow specialization and
reveals an evolutionary advantage offered by polymorphic regulation .
Regulatory diversity is likely to be a significant contributor to
complexity in a bacterial world in which multiple sigma factors are a
universal feature .
Activity of OPT-80, a Novel Macrocycle, Compared with Those of Eight Other Agents against Selected Anaerobic Species. Kim L. Credito, 2004.Agar dilution MIC was used to compare activities of OPT-80, linezolid, vancomycin, teicoplanin, quinupristin/dalfopristin, amoxicillin/clavulanate, imipenem, clindamycin, and metronidazole against 350 gram-positive and -negative anaerobes . OPT-80 was active against gram-positive strains only, especially Clostridium spp . (85 strains tested, including 21 strains of C . difficile), with MICs ranging between  0.016 and 0.25 µg/ml .
Mapping of Genomic Regions (Quantitative Trait Loci) Controlling Production and Quality in Industrial Cultures of the Edible Basidiomycete Pleurotus ostreatus. Luis M. Larraya, 2003.Industrial production of the edible basidiomycete Pleurotus ostreatus (oyster mushroom) is based on a solid fermentation process in which a limited number of selected strains are used . Optimization of industrial mushroom production depends on improving the culture process and breeding new strains with higher yields and productivities . Traditionally, fungal breeding has been carried out by an empirical trial and error process . In this study, we used a different approach by mapping quantitative trait loci (QTLs) controlling culture production and quality within the framework of the genetic linkage map of P . ostreatus . Ten production traits and four quality traits were studied and mapped . The production QTLs identified explain nearly one-half of the production variation . More interestingly, a single QTL mapping to the highly polymorphic chromosome VII appears to be involved in control of all the productivity traits studied . Quality QTLs appear to be scattered across the genome and to have less effect on the variation of the corresponding traits . Moreover, some of the new hybrid strains constructed in the course of our experiments had production or quality values higher than those of the parents or other commercial strains . This approach opens the possibility of marker-assisted selection and breeding of new industrial strains of this fungus .
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