Microbial Succession and Nitrogen Cycling in Cultured Biofilms as Affected by the Inorganic Nitrogen Availability

Abstract

Biofilms play important roles in nutrients and energy cycling in aquatic ecosystems. We hypothesized that as eutrophication could change phytoplankton community and decrease phytoplankton diversity, ambient inorganic nitrogen level will affect the microbial community and diversity of biofilms and the roles of biofilms in nutrient cycling. Biofilms were cultured using a flow incubator either with replete inorganic nitrogen (N-rep) or without exogenous inorganic nitrogen supply (N-def). The results showed that the biomass and nitrogen and phosphorous accumulation of biofilms were limited by N deficiency; however, as expected, the N-def biofilms had significantly higher microbial diversity than that of N-rep biofilms. The microbial community of biofilms shifted in composition and abundance in response to ambient inorganic nitrogen level. For example, as compared between the N-def and the N-rep biofilms, the former consisted of more diazotrophs, while the latter consisted of more denitrifying bacteria. As a result of the shift of the functional microbial community, the N concentration of N-rep medium kept decreasing, while that of N-def medium showed an increasing trend in the late stage. This indicates that biofilms can serve as the source or the sink of nitrogen in aquatic ecosystems, and it depends on the inorganic nitrogen availability.

Host Age Affects the Development of Southern Catfish Gut Bacterial Community Divergent From That in the Food and Rearing Water

“…This allows us to speculate that the increased microbial diversity is independent of host species during the development. Two other studies aimed to explore the associations between developing hosts, showing the microbial diversity of significant decreases in zebrafish (Zac Stephens et al, 2016 ) and increases in gibel carp (Li et al, 2017 ). The resulting differences are possibly attributed to food shifts and different living environments at several critical stages throughout the lifespan of the hosts (Penders et al, 2006 ).…”

“…In recent years, some studies focus on early developmental gut microbiota in fish. Specifically, the studies of a model organism, zebrafish, ( Danio rerio ) (Jemielita et al, 2014 ; Burns et al, 2016 ; Zac Stephens et al, 2016 ) as well as several commercial species are performed such as cod ( Gadus morhua ) (Bakke et al, 2015 ), channel catfish ( Ictalurus punctatus ) (Bledsoe et al, 2016 ) and gibel carp ( Carassius auratus gibelio ) (Li et al, 2017 ). The previous studies consistently indicate that the gut microbial assemblages change over time.…”

“…But it should be noted that the changes are possibly related to different food supplies to the hosts during their development. Therefore the process of gut microbial assemblages is likely to be affected by diet shifts, for example from live feeds to commercial feeds, and even affected by interactive effects between host age and diet (Bakke et al, 2015 ; Bledsoe et al, 2016 ; Li et al, 2017 ).…”

“…Due to the restrictions on early food resource availability and gut development, it is unavoidable for newly hatched individuals to be faced with different food resources over ontogenesis. This phenomenon is common to larva culture of commercial fish species which are usually fed on live feeds as transitional foods, such as water earthworm, fairy shrimp, copepod, rotifer or artemia, and subsequently the diets were switched to commercial feeds (Bakke et al, 2015 ; Bledsoe et al, 2016 ; Li et al, 2017 ). One recent experiment was designed to overcome age-related dietary effects by Wong et al ( 2015 ) who used developing zebrafish fed on one artificial diet on long-term basis to explore age-specific gut microbial assemblages.…”

Comparison of the bacterial and methanotrophic diversities between an Italian paddy field and its neighboring meadow

“…The recently isolated Fimbriimonas ginsengisoli within the Fimbriimonadia class was described as strictly aerobic, Gram-negative, meso- and neutrophilic strain with the ability to grow on peptone, casamino acids and yeast extract (Im et al ., 2012). In another study, genera affiliated with the Fimbriimonadaceae grew better in biofilms cultured using a flow incubator with supplied inorganic nitrogen (N) conditions compared to deficient N (Li et al ., 2017). Since the paddy field more similarly resembles an N condition, it could explain Fimbriimonadaceae’s higher abundance compared to the meadow and moreover, the higher diversity of microbial community observed in the paddy field (Figure 3).…”