Small proteins (SPs) are known players in bacterial lifestyle \cite{Santos2013}. They are essential in a diversity of molecular functions, assuming a vast number of different roles. Among such purposes, for instance, one can cite regulation of alternative factor sigma use, mediation of protein-protein interaction, driving membrane curvature, DNA translation, and are essential virulence factors. Another remarkable role attributed to a class of SPs is its use by eukaryotes and prokaryotes cells as a defense mechanism. In that case, we reference such class of SPs as AntiMicrobial Proteins (AMPs). However, a defense mechanism for a bacterial organism allowing it to overwhelm a previous well-established population of microbes numerically could be though as an infection. Under this circumstance, a defense mechanism also plays a fundamental role as a virulence factor. Despite their importance, we continue to under represent SPs in genome annotations due to limitations in the current state of art process of identification of novel genes: since SPs are smallest, it means that the better gene prediction programs will no consider ground gene predictions of small portions of DNA sequences and frequently ignore them. Despite the weakness of computer aid predictions of SPs, we had some success on their annotation via transcriptome studies. In this study, we hypothesize that SPs are crucial as virulence factors for several bacterial species. To prove such statement, we made predictions of virulence factors of 40 genomes, by four different software, and correlated the size of proteins with their virulence prediction. We conclude that this hypothesis is not ground because it didn't resist this simple assessment.
Results