Mean number of rRNA operons in early- and late-appearing soil bacterial isolates

Range early appearing 5.5: late appearing 1.4 rRNA operon copies
Organism bacteria
Reference Klappenbach JA, Dunbar JM, Schmidt TM. rRNA operon copy number reflects ecological strategies of bacteria. Appl Environ Microbiol. 2000 Apr66(4):1328-33. p.1330 left column 4th paragraphPubMed ID10742207
Method p.1330 left column 4th paragraph:"Response time of soil isolates and rRNA operon copy number: To test whether rRNA operon copy number is correlated with the response time (a function of µmax and L) of bacterial populations in soil to resource availability, heterotrophic bacteria appearing early and late on agar media were isolated from soils from an agricultural research site in Michigan and a rice paddy near Sendai, Japan (ref 16) (Fig. 1A). Early-appearing isolates possessed, on average, a significantly greater number of rRNA operons (x=5.5 copies) than late-appearing isolates (x=1.4 copies) (Fig. 1B). Of the early-appearing isolates, 6 of 11 contained five or more copies of the rRNA operon per genome, while 12 of 13 late-appearing species contained two or fewer copies."
Comments p.1330 left column 3rd paragraph:"In environments with periodic resource fluctuations, lag time (L, the time before initiation of cell division) and maximal growth rate (µmax) are important components of fitness (refs 21, 34). Populations that can rapidly achieve high maximal growth rates (short L, high µmax) are able to utilize available resources before competing populations. In contrast, lag time does not impose a fitness advantage in environments with a constant supply of resources (refs 18, 32). Multiple rRNA operons allow transcriptional initiation from multiple loci, permitting a rapid increase in the intracellular concentration of rRNA, thereby effectively decreasing lag time. A potential tradeoff for a rapid up-shift capacity is the metabolic expense of rRNA overproduction at low growth rates, apparently due to inadequate regulation of rRNA operons (ref 30). In agreement with these observations, bacteria isolated from low-nutrient aquatic environments share the characteristics of slow growth and few (typically one to two) rRNA operons (refs 7, 13)."
Entered by Uri M
ID 111694