Roles and interactions of two methylotrophic bacterial strains in the development of a marine denitrifying biofilm

硝酸盐是一种高度可溶的分子，可以迅速扩散到地表水和地下水中，从而污染饮用水。这种化合物会导致河流和湖泊的富营养化，以及河口和海洋环境中有害的藻类水华。硝酸盐是由含氮化合物的硝化作用产生的，或来自人类活动，如农业施肥。硝酸盐可以通过被称为反硝化的微生物过程传播。当硝酸盐而不是氧气被用作细菌呼吸的电子受体，最终产生分子氮(N2)时，就会发生这种情况。反硝化细菌存在于各种水环境中，无论是在淡水中还是在海水中。废水处理系统中可以包括反硝化过程，以防止有害的过量硝酸盐在环境中释放。 蒙特利尔生物穹顶经营着一个闭路水族馆，里面有300万升海水，里面有大型动物和无脊椎动物。为了控制硝酸盐水平，使用了反硝化生物反应器。我的团队研究这个生物反应器的微生物学已经有10多年了，目的是提高它的效率。反硝化是通过生长在其中的多种微生物生物膜来实现的。从这一生物膜中，我们分离出了两种具有相应反硝化活性的主要细菌：扎瓦茨亚微生物菌NL23和甲基噬菌属。菌株JAM1，占生物被膜的70%~80%。这项建议是为了了解这两个物种如何共同努力，在生物膜中实现高效的反硝化作用。 大多数天然生物膜是由Biodome反硝化生物系统中发现的混合物种组成的。研究这种复杂的生物膜是一个挑战，因为每一个物种都会影响生物膜的发展。了解菌株JAM1和NL23是如何发展成为生物膜的，将揭示形成混合物种微生物生物膜的一些机制。最后，将获得与在反硝化条件下生长的海洋甲基营养细菌的作用机制有关的新信息。

Nitrate is a highly soluble molecule that can rapidly diffuse in surface waters and groundwaters, and thus contaminate drinking water. This compound contributes to rivers' and lakes' eutrophication and harmful algal blooms in estuarine and marine environments. Nitrate is produced from nitrification of nitrogen-containing compounds or originates from anthropogenic activities such as agricultural fertilization. Nitrate can be disseminated through microbial process called denitrification. This occurs when nitrate is used as an electron acceptor, instead of oxygen, for bacterial respiration, to ultimately produce molecular nitrogen (N2). Denitrifying bacteria are found in a variety of aquatic environments, either in fresh water or seawater. A denitrification process can be included in wastewater treatment systems to prevent environmental release of detrimental nitrate excess The Montreal Biodome operates a closed circuit aquarium of 3 million liters of seawater containing large animals and invertebrates. To control nitrate levels, a denitrification bioreactor is used. My team has studied the microbiology of this bioreactor for more than 10 years aiming to improve its efficiency. The denitrification is achieved by a multi-species microbial biofilm growing in it. From this biofilm, we have isolated the two main bacterial species carrying relevant denitrifying activities: Hyphomicrobium zavarzinii strain NL23 and Methylophaga sp. strain JAM1, which account for 70 to 80% of the biofilm. This proposal is to understand how these two species work together to achieve efficient denitrification in the biofilm. Most natural biofilms are composed of mixed species as the one found in the Biodome denitrifying biosystem. Studying such complex biofilms is a challenge, as each species can influence the biofilm development. Understanding how strains JAM1 and NL23 develop into the biofilm will unravel some of the mechanisms shaping mixed-species microbial biofilms. Finally, novel information related to mechanisms of action of marine methylotrophic bacteria grown under denitrifying conditions will be obtained.