We found that all genes in the fhuCDBG Reversine supply operon encoding a siderophore-dependent iron transporter were up-regulated at 40uC at mid-logarithmic and/ or late logarithmic phases. These findings are analogous to data reported previously for the homologous ftsABCD operon in GAS grown at 40uC. The homologue of the GAS mtsABC operon was up-regulated 2- to 2.3-fold at 40uC relative to 30uC. MtsABC is involved in ferric and manganese ion U0126 in vivo uptake in several low GC% gram-positive bacteria, and plays a role in GAS stress resistance and virulence. A third putative operon involved in iron uptake and transport in S. mutans was also up-regulated 1.7 to 2.1 at 40uC in GBS, as were two other genes, gbs0563 and gbs1112, both encoding iron-sulfur clusterbinding proteins. In addition, we found that genes implicated in nickel metabolism, were also up-regulated at high temperature. Conversely, and consistent with these data, gbs1749 encoding an iron-dependent repressor was down-regulated at 40uC relative to 30uC. The need of iron by bacteria in vivo during infection when the amount of free iron is low is well known. Our results indicate that the expression of iron metabolism genes also is increased in GBS in response to elevated temperature, as observed for GAS and Escherichia coli. Expression microarray analysis was performed with a custommade Affymetrix chip formulated based on the genome sequence of strain NEM316. The chip contains 1,995 probe sets corresponding to the annotated ORFs in this genome. Briefly, end-labeled cDNA was hybridized overnight at 40uC using the Affymetrix hybridization and staining modules, according to the manufacturer��s instructions. Chip hybridization data were acquired and normalized using Affymetrix GeneChip Operating Software. Hybridization intensity values were normalized to the mean intensity of all GBS genes present on the chip using GCOS version 1.0 to permit comparison of data obtained from multiple experimental conditions. Only genes with a ����present���� signal were analyzed further. Data obtained from biological replicates of each experimental condition derived from three independent cultures were used in the analysis. A principal component analysis was performed using the Partek Pro 6.0 package, and a visualization system was used to assess microarray quality and array-to-array variability. Input information combined hybridization intensity values and information about sample preparation and hybridization. An ORF was considered to be differentially expressed at 30uC or 40uC if there was a significant change in expression greater than 2-fold at one or more time points. ArrayAssist software v5.5 was used to perform analyses and generate graphs. The microarray data of this study have been deposited in the Gene Expression Omnibus database. Soil plays a crucial role in determining the rates and the diversity of ecosystem processes.