Activity of ammonia-oxidizing bacteria in enriched cultures exposed to 3,4-dimethyl-1H-pyrazole dihydrogen phosphate nitrification inhibitor

The use of nitrification inhibitors is an interesting tool to achieve a higher N efficiency in plants while decreasing the environmental impact of N fertilization. However, an integrated evaluation of the efficiency of nitrification inhibitors over time, understood as the period in which the nitrifying activity is inhibited or slows down, is necessary to assess whether their use is ecofriendly and sustainable. To test the direct efficiency of 3,4-dimethyl-1H-pyrazole dihydrogen phosphate (DMPP) on nitrification, a study has been carried out in two cultures enriched with ammonia-oxidizing bacteria (AOB) obtained from a soil with continuous N fertilization (80 kg N ha−1 year−1 as NH4NO3) and from soil without N fertilization. In addition, Cu has been evaluated as a cofactor of ammonia monoxygenase, a key enzyme in the nitrifying activity of AOBs. On the other hand, the stability of DMP has been studied both in the cultivation system enriched in AOBs and in soil to assess the efficiency of the inhibitor due to its persistence over time. Our work reveals that nitrification rates observed in cultures enriched in AOBs from genus Nitrosospira isolated from soils with continuous N fertilization were not higher than those of cultures without N fertilization. In AOB cultures, DMPP was a very efficient inhibitor of nitrification (> 50 % inhibition of integrated AMO activity), mainly due to the stability of DMP (3,4-dimethyl-1 H-pyrazole) in the cultures. However, DMP stability was significantly lower under soil conditions (> 90 % of DMP was degraded in the first 30 days of incubation). Other metals are suggested as cofactors of the enzyme ammonia monooxygenase alternatively to Cu.This work was supported by Spanish Government-Ministry of Science, Innovation and Universities (RTI2018-094623-B-C22), Spain. MCIN/AEI/10.130039/501100011033/FEDER, EU. J.M.R. was supported by a doctoral fellowship from Coordination for the Improvement of Higher Education Personnel (CAPES), of Brazilian Government (1I11903/13-9), Brazil. Open access funding provided by the Public University of Navarra

Analise taxonomica em Leuconostoc oenos.Uma perspectiva polifasica.

A poly phasic approach was applied to reclassify Leuconostoc oenos in a new genus and to establish its taxonomic organization at the infra generic level. The universe of strains included isolates from Portuguese red wines and reference strains belonging to that species and to other groups of lactic acid bacteria, namely Leuconostoc spp., Pediococcus spp. and Lacto bacillus spp.. Experimental work began with strain isolation and optimization of growth conditions for L. oenos strains, in order to select a suitable p H and culture medium. Representativeness analysis of isolation procedures and data from antibiotic resistance patterns led to the proposal of five media for the selective isolation of different lactic acid bacteria. An optimization index is also proposed to integrate the effect of a selected factor over the parameters describing a growth curve. Strain identification at genus and species level was based on the global evaluation of dichotomous keys, bayesian approaches and dendrograms, using reference strains. Analysis of taxonomic characters, usually described as diagnostic for the taxa under study, clearly revealed its reduced reliability and pointed out the need of real diagnostic ones. In order to obtain phenetics characters useful to discriminate L. oenos strains from the other leuconostoc and to validate its allocation to a new genus, electrophoretic protein patterns, metabolic fingerprints with BIOLOG, antibiotic resistance patterns and enzymatic profiles by API Zym were performed...Available from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1249-074 Lisboa, Portugal / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga

Listeria monocytogenes Biofilm-Associated Protein (BapL) May Contribute to Surface Attachment of L. monocytogenes but Is Absent from Many Field Isolates▿

Listeria monocytogenes is a food-borne pathogen capable of adhering to a range of surfaces utilized within the food industry, including stainless steel. The factors required for the attachment of this ubiquitous organism to abiotic surfaces are still relatively unknown. In silico analysis of the L. monocytogenes EGD genome identified a putative cell wall-anchored protein (Lmo0435 [BapL]), which had similarity to proteins involved in biofilm formation by staphylococci. An insertion mutation was constructed in L. monocytogenes to determine the influence of this protein on attachment to abiotic surfaces. The results show that the protein may contribute to the surface adherence of strains that possess BapL, but it is not an essential requirement for all L. monocytogenes strains. Several BapL-negative field isolates demonstrated an ability to adhere to abiotic surfaces equivalent to that of BapL-positive strains. BapL is not required for the virulence of L. monocytogenes in mice