Allison N. Evans Maureen K. Wright-Osment James L. Zajicek Scott A. Heppell Stephen C. Riley Charles C. Krueger Donald E. Tillitt Catherine A. Richter 2012 Thiamine (vitamin B₁) deficiency is a global concern affecting wildlife, livestock, and humans. In Great Lakes salmonines, thiamine deficiency causes embryo mortality and is an impediment to restoration of native lake trout (<i>Salvelinus namaycush</i>) stocks. Thiamine deficiency in fish may result from a diet of prey with high levels of thiaminase I. The discoveries that the bacterial species <i>Paenibacillus thiaminolyticus</i> produces thiaminase I, is found in viscera of thiaminase-containing prey fish, and causes mortality when fed to lake trout in the laboratory provided circumstantial evidence implicating <i>P. thiaminolyticus</i>. This study quantified the contribution of <i>P. thiaminolyticus</i> to the total thiaminase I activity in multiple trophic levels of Great Lakes food webs. Unexpectedly, no relationship between thiaminase activity and either the amount of <i>P. thiaminolyticus</i> thiaminase I protein or the abundance of <i>P. thiaminolyticus</i> cells was found. These results demonstrate that <i>P. thiaminolyticus</i> is not the primary source of thiaminase activity affecting Great Lakes salmonines and calls into question the long-standing assumption that <i>P. thiaminolyticus</i> is the source of thiaminase in other wild and domestic animals. application/pdf 10.1139/f2012-043 en NRC Research Press <i>Paenibacillus thiaminolyticus</i> is not the cause of thiamine deficiency impeding lake trout (<i>Salvelinus namaycush</i>) recruitment in the Great Lakes article