Relationship between nitrate/nitrite reductase activities in meat associated staphylococci and nitrosylmyoglobin formation in a cured meat model system

Quantitative determination of catalase, nitrate reductase, nitrite reductase and nitric oxide synthase activities (NOS) was performed on I I different bacterial strains, mainly staphylococci, isolated from fermented sausages, bacon brine or cured meat products. All except one strain possessed catalase activity in the range from 1.0 to 6.1 mu mol min(-1) ml(-1). Ten out of I I bacteria strains showed nitrate reductase activity in the range between 50 and 796 nmol min(-1) ml(-1) and nine showed nitrite reductase activity in the range between 6 and 42 nmol min(-1) ml(-1). No evidence of NOS activity of the selected strains was detected. In a colour formation assay containing myoglobin all strains affected nitrosylmyoglobin (MbFe(II)NO) formation in assays containing nitrite, whereas only strains having nitrate reductase activity generated MbFe(II)NO in assays containing nitrate as the sole nitrosylating agent. The quantitative nitrate and nitrite reductase activity did not fully explain or correlate well with the observed rate of formation of MbFe(II)NO, which seemed to be more affected by the growth rate of the different strains. The mechanism of the reduction of nitrite into NO of strains not having nitrite reductase activity remains to be fully elucidated, but could be due to a dual-mode action of nitrate reductase capable of acting on nitrate. (c) 2007 Elsevier B.V. All rights reserved.