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Other bacteria have been shown to create isovaleric acid, and may contribute to the production of it in beer in unsanitary conditions. ''Bacillus amyloliquefaciens'' and ''B. atrophaeus'' are Gram-positive, aerobic (require oxygen for growth) bacteria and have been shown to produce isovaleric acid <ref name="Vasquez">[http://bashanfoundation.com/gmaweb/pdfs/vazquez1.pdf Phosphate-solubilizing microorganisms associated with the rhizosphere of mangroves in a semiarid coastal lagoon. P. Vazquez, G. Holguin, M.E. Puente, A. Lopez-Cortes, Y. Bashan. 2000.]</ref><ref>[http://web.mst.edu/~microbio/BIO221_1998/B_amylo.html Bacillus amyloliquifaciens. Carl Sather's website. Retrieved 10/06/2015.]</ref><ref>[http://www.researchgate.net/publication/263432119_Bacillus_atrophaeus_main_characteristics_and_biotechnological_applications__a_review Bacillus atrophaeus: main characteristics and biotechnological applications – a review. Sandra R B R Sella, Luciana Vandenberghe, Carlos Ricardo Soccol. 2014.]</ref>. ''Xanthobacter agilis'' is a Gram-negative aerobic bacteria that can produce isovaleric acid <ref name="Vasquez"></ref><ref>[http://www.thelabrat.com/restriction/sources/Xanthobacteragilis.shtml Xanthobacter agilis. The Lab Rat. Retrieved 10/06/2015.]</ref>. ''Paenibacillus macerans'' is a facultative anaerobe (can utilize oxygen if present, but oxygen is not required) that can produce isovaleric acid. ''P. macerans'' is a Gram-variable bacteria, meaning that it can produce Gram-positive and Gram-negative rods <ref>[https://en.wikipedia.org/wiki/Paenibacillus_macerans Paenibacillus macerans. Wikipedia. Retrieved 10/06/2015.]</ref>.