Gene expression of Porphyromonas gingivalis ATCC 33277 when growing in an in vitro multispecies biofilm

The aim of the present study to compare the transcriptomic profile of P.gingivalis when growing within an in vitro multispecies biofilm or in a planktonic state, using microarray technology. P. gingivalis ATCC 33277 was grown in anaerobiosis within multi-well culture plates at 37ºC for 96h under two conditions: (a) planktonic samples (no hydroxyapatite discs) or (b) within a multispecies-biofilm containing Streptococcus oralis, Actinomyces naeslundii, Veillonella parvula, Fusobacterium nucleatum and Aggregatibacter actinomycetemcomitans deposited on hydroxyapatite discs. Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM) combined with Fluorescence In Situ Hybridization (FISH) were used to verify the formation of the biofilm and the presence of P. gingivalis in it. Total RNA was extracted from both the multispecies biofilm and planktonic samples, then purified and, with the use of a microarray, its differential gene expression was analyzed. A linear model was used for determining the differentially expressed genes using a filtering criterion of two fold change (up or down) and a significance p-value of <0.05. Differential expression was confirmed by reverse transcription quantitative polymerase chain reaction (RTqPCR).