Aquarium Nitrification Revisited: Thaumarchaeota Are the Dominant Ammonia Oxidizers in Freshwater Aquarium Biofilters

Abstract

Ammonia-oxidizing archaea (AOA) outnumber ammonia-oxidizing bacteria (AOB) in many terrestrial and aquatic environments. Although nitrification is the primary function of aquarium biofilters, very few studies have investigated the microorganisms responsible for this process in aquaria. This study used quantitative real-time PCR (qPCR) to quantify the ammonia monooxygenase (amoA) and 16S rRNA genes of Bacteria and Thaumarchaeota in freshwater aquarium biofilters, in addition to assessing the diversity of AOA amoA genes by denaturing gradient gel electrophoresis (DGGE) and clone libraries. AOA were numerically dominant in 23 of 27 freshwater biofilters, and in 12 of these biofilters AOA contributed all detectable amoA genes. Eight saltwater aquaria and two commercial aquarium nitrifier supplements were included for comparison. Both thaumarchaeal and bacterial amoA genes were detected in all saltwater samples, with AOA genes outnumbering AOB genes in five of eight biofilters. Bacterial amoA genes were abundant in both supplements, but thaumarchaeal amoA and 16S rRNA genes could not be detected. For freshwater aquaria, the proportion of amoA genes from AOA relative to AOB was inversely correlated with ammonium concentration. DGGE of AOA amoA genes revealed variable diversity across samples, with nonmetric multidimensional scaling (NMDS) indicating separation of freshwater and saltwater fingerprints. Composite clone libraries of AOA amoA genes revealed distinct freshwater and saltwater clusters, as well as mixed clusters containing both freshwater and saltwater amoA gene sequences. These results reveal insight into commonplace residential biofilters and suggest that aquarium biofilters may represent valuable biofilm microcosms for future studies of AOA ecology.

Significance of archaeal nitrification in hypoxic waters of the Baltic Sea

“…The relative contributions to ammonia oxidation by autotrophic AOA and ammonia-oxidizing bacteria (AOB) have been inferred using the archaeal and bacterial amoA genes that encode subunit A of the key enzyme ammonia monooxygenase (see, for example, Rotthauwe et al, 1997;De Corte et al, 2009;Sauder et al, 2011;Auguet et al, 2012). These studies often revealed the dominance of archaeal over bacterial ammonia oxidizers (Francis et al, 2005;Wuchter et al, 2006;Mincer et al, 2007;Agogué et al, 2008;Newell et al, 2013).…”

Cultivo e filogenia molecular de Archaea a partir de amostras de aquário de água doce

“…Porém, existe a proposição da sua inserção no Estudos vem evidenciando a importância desses microrganismos no ciclo do nitrogênio não apenas em ambientes terrestres, mas também em ambientes aquáticos (Sauder et al, 2011;Hatzenpichler, 2012), e sugerem a obtenção de culturas laboratoriais destes organismos como instrumento chave para elucidação de aspectos fisiológicos, entre outros.…”

“…Existem poucos estudos com o objetivo de investigar os microrganismos envolvidos no processo de nitrificação em filtros de aquários (Sauder et al, 2011;Urakawa et al, 2008), sendo a maioria realizados com organismos do Domínio Bacteria (DeLong & Hovanec, 1996;Grommen et al, 2005;Bagchi et al, 2014). …”

“…Estabelecida a ubiquidade deste domínio, representantes já foram descritos em uma variedade de ambientes, incluindo solos (Ochsenreiter et al, 2003;Catão et al, 2013), ambientes aquáticos (Francis et al, 2005), esgotos (Sun et al, 2014) e ambientes poluídos (Damashek et al, 2015), sistemas de distribuição e tratamento de água (Van der Wielen et al, 2009) aquários residenciais (Urakawa et al, 2008;Sauder et al, 2011) e em diversas partes do corpo humano.…”

“…Estudos vem evidenciando a importância desses microrganismos no ciclo do nitrogênio não apenas em ambientes terrestres, mas também em ambientes aquáticos (Sauder et al, 2011;Hatzenpichler, 2012), e sugerem a obtenção de culturas laboratoriais destes organismos como instrumento chave para elucidação de aspectos fisiológicos, entre outros. (Leigh, 2000) e processos de desnitrificação (Philippot, 2002;Offre et al, 2013 (Herrmann et al 2012), solos ácidos (Zhang et al, 2012) e outros ambientes aquáticos (Hong et al, 2013).…”