Probiotics are live microorganisms known to confer a host benefit when ingested and represent a feasible option to alleviate gastrointestinal microbiota imbalances. Alleviation may occur via several mechanisms including bacteriocin production by probiotics to limit pathogen colonization. Unfortunately, probiotic efficacy may be restricted by their inability to incorporate into the naturally- occurring, static biofilms lining the human gut. This thesis examines the biofilm forming ability of fourteen commercial probiotic strains via a high-throughput crystal violet assay and scanning electron microscopy. All probiotics formed biofilms in vitro in at least one condition tested. More specifically, strong biofilm formation was observed by Pediococcus acidilactici under several conditions. Further investigation demonstrated that both anaerobiosis and bacteriocin production alter P. acidilactici biofilm formation. Moreover, it was shown that aeration, medium, and mode of growth modify bacteriocin production from P. acidilactici, highlighting the importance of environmental factors that influence both biofilm formation and bacteriocin production.