Principal Component Analysis for Bacterial Proteomic Analysis Y-h. Taguchi 1,⋆ and Akira Okamoto 2 1 Department of Physics, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan 2 Department of School Nursing and Health, Aichi University of Education, 1 Hirosawa, Igaya-cho, Kariya, Aichi 448-8542, Japan Abstract. Proteomic analysis is a very useful procedure to understand the bacterial behavioural responses to the external environmental fac- tors. This is because bacterial genome information is mainly devoted to code enzyme for the control of the cellular metabolic networks. In this paper, we have performed proteomic analysis of Streptococcus pyogenes, which is known to be flesh-eating bacteria and can cause several human life-threatening diseases. Its proteome during growth phase is measured for four time points under two different culture conditions; with or with- out shaking. Its purpose is to understand the adaptivity to oxidative stresses. Principal component analysis is applied and turns out to be useful to depict biologically important proteins for both supernatant and cell components. Keywords: Streptococcus pyogenes, proteomic analysis, principal com- ponent analysis. 1 Introduction Streptococcus pyogenes is an important pathogen. The estimated annual number of Streptococcus pyogenes infection cases are more than 700 million. There are over 650,000 cases of severe, invasive infections that have a mortality rate of 25 %. Although S. pyogenes is a normal bacteria flora, occasionally S. pyogenes can also cause life-threatening diseases. This means, it will be important to know what triggers the diseases that S. pyogenes causes. There are a huge number of researches [2] that investigate transcrptome responses to external environmental factor, but there are very few researches on how its proteome changes in response to external stimulations. In this paper, we have systematically compared proteome of S. pyogenes dur- ing growing phases under two distinct culture conditions; with or without shak- ing. The latter condition was designed to be more oxidative stress condition. The purpose of this research is to know the proteomic response to these two differ- ent growth conditions. Using the principal component analysis (PCA) [12], we have selected representative proteins. Many of the representative proteins play biological roles during the incubation. ⋆ Corresponding author. T. Shibuya et al. (Eds.): PRIB 2012, LNBI 7632, pp. 141–152, 2012. c  Springer-Verlag Berlin Heidelberg 2012