The human gut microbiome plays a vital role in supporting gastrointestinal health. Bacteroidales, an important group of bacteria in the gut microbiome, possess a distinct contractile injection system (CIS) called Bacteroidales injection systems (BIS). BIS genes are remarkably prevalent. They are found in approximately 99% of healthy adult gut microbiomes in Western populations while individuals suffering from inflammatory bowel diseases (IBD), such as Crohn’s disease and ulcerative colitis, exhibit significantly reduced levels of these genes. Our aim is to elucidate BIS as an important group of CIS in the human gut microbiome. To do so, we study BIS expression in vitro in B. cellulosilyticus WH2. We take a biochemical and genetic regulation approach to characterize the BIS. Through western blot of important structural proteins, we confirm protein detection of the phage-like sheath of BIS. Using RNAseq, we identified a BIS promoter and use a luciferase plasmid reporter screen to identify potential transcription factors of BIS. We investigate carbon sources that correlate with higher BIS gene levels and demonstrate increase in structure protein detection. Together, these data form the first descriptions of a novel CIS group in the human gut microenvironment and pave the way to investigating its role in human gut health.