BMC Genomics 2006, 7:154 http://www.biomedcentral.com/1471-2164/7/154 TFhigeutrimee2 points chosen for cDNA library construction The time points chosen for cDNA library construction. The diagram illustrates when, in the context of the symbiont- induced developmental program of the host light organ and major milestones in V. fischeri colonization, tissues for library con- struction were dissected from juvenile animals. As the symbionts aggregate, migrate into host tissues and take up residence in the light organ crypts, they induce the diagrammed series of developmental changes in the various components of the organ. Most of these changes, including the irreversible loss of the SCE, which doesn't culminate until 96 hours, are triggered by or around 12 hours following first exposure to environmental V. fischeri. In addition, around 12 hours, the symbionts usually fully colonize the crypt spaces and their growth is attenuated and luminescence induced. By 48 hours, significant changes in the pro- teome occur (Lemus and McFall-Ngai, 2000). In addition, mutants of V. fischeri incapable of persisting in the light organ lose the ability to colonize the organ beginning at around 48 hours. unknown protein. Of the remaining 30% without a signif- icant BLAST hit, nearly half, 46% (1,963), may represent novel sequences because there was no hit to the non- redundant database. Using the DAVID program, GO terms for biological proc- ess, molecular function and cellular component were associated with 75% (4,527) of the 6,061 ESTs that hit with an annotated protein in the NCBI database (Fig. 4 and see Additional files 1, 2 and 3). Of these 4,527 ESTs, 78% (3,512) have an associated biological process description, 90% (4,071) have an associated molecular function description, and 65% (2,960) have an associated cellular component description. Of the 13,962 ESTs, the largest number of ESTs (3,039) was found to be specific to the 48-h symbiotic library and this number is nearly twice the number found to be spe- cific from any other library (1,311 specific to the hatchling library, 1,381 specific to the 12-h aposymbiotic library, 1,314 specific to the 48-h aposymbiotic library, and 1,699 specific to the 12-h symbiotic library). In addition, 29% (4,006) of the 13,962 ESTs are sequences derived from only aposymbiotic libraries (1,311 from hatchling librar- Page 4 of 10 (page number not for citation purposes)