Strain‐specific consumption and transformation of alga‐derived dissolved organic matter by members of the Limnohabitans‐C and Polynucleobacter‐B clusters of Betaproteobacteria

Abstract

We investigated changes in quality and quantity of extracellular and biomass-derived organic matter (OM) from three axenic algae (genera Rhodomonas, Chlamydomonas, Coelastrum) during growth of Limnohabitans parvus, Limnohabitans planktonicus and Polynucleobacter acidiphobus representing important clusters of freshwater planktonic Betaproteobacteria. Total extracellular and biomass-derived OM concentrations from each alga were approximately 20 mg l and 1 mg l respectively, from which up to 9% could be identified as free carbohydrates, polyamines, or free and combined amino acids. Carbohydrates represented 54%-61% of identified compounds of the extracellular OM from each alga. In biomass-derived OM of Rhodomonas and Chlamydomonas 71%-77% were amino acids and polyamines, while in that of Coelastrum 85% were carbohydrates. All bacteria grew on alga-derived OM of Coelastrum, whereas only Limnohabitans strains grew on OM from Rhodomonas and Chlamydomonas. Bacteria consumed 24%-76% and 38%-82% of all identified extracellular and biomass-derived OM compounds respectively, and their consumption was proportional to the concentration of each OM compound in the different treatments. The bacterial biomass yield was higher than the total identifiable OM consumption indicating that bacteria also utilized other unidentified alga-derived OM compounds. Bacteria, however, also produced specific OM compounds suggesting enzymatic polymer degradation or de novo exudation.

Effects of stocking density on the growth performance, physiological response and intestinal microbiota of juvenile Echiura worms ( Urechis unicinctus )

“…Burkholderiales and Limnohabitans , which were enriched in the intestinal samples of U. unicinctus juveniles from the 2,000 U group, can also degrade sugar and organic matter (Horňák, Kasalický, Šimek, & Grossart, 2017; Lin, Hobson, & Wertz, 2016). However, the activities of intestinal digestive enzymes were significantly decreased as the stocking density increased from 1,000 U to 2,000 U. SOD, GSH‐PX and CAT are typical antioxidant enzymes responsible for protecting organisms from oxidative damage, through the elimination of excess reactive oxygen species (Homayounitabrizi, Asoodeh, & Soltani, 2017).…”

Bacterial Community of the Rice Floodwater Using Cultivation-Independent Approaches

“…Polynucleobacter members often dominate planktonic freshwater communities [ 58 ], where pH, conductivity, and dissolved organic carbon concentration play an important role in colonization [ 59 ]. Also, flagellate grazing and the consumption of low molecular weight substrates are related to the survival of Polynucleobacter in freshwater environments [ 60 , 61 ].…”

Ecological Differentiation in Two Major Freshwater Bacterial Taxa Along Environmental Gradients

“…Interconnections with these and other eukaryotes may also harbor different qualities of interactions besides predator-prey relationships, such as utilization of eukaryotic exudates by bacteria (Simek et al, 2011;Horňák et al, 2017). For PnecB, which shows the strongest interconnection of the Polynucleobacter subclusters in our network, it was demonstrated that they grew on organic matter derived by chlorophyte taxa, i.e., Coelastrum reticulatum (Horňák et al, 2017). Our results do not show a connection of PnecB2 and Chlorophyta but with other eukaryotic groups that comprise exudate releasing taxa.…”

“…Among biotic factors, protists may shape bacterial communities through grazing (Grujcic et al, 2018) and exudation of organic matter (Horňák et al, 2017). Specifically, culture-based experiments demonstrated that Polynucleobacter and Limnohabitans strains (LimC, PnecC, and LimB) were preyed on preferentially by flagellates (Šimek et al, 2013;Grujcic et al, 2018).…”

“…Some Limnohabitans strains use algal derived organic material as substrate source and show specific substrate utilization characteristics in batch cultures (Simek et al, 2010;Kasalický et al, 2013). In growth experiments on organic matter derived from three axenic algae (genera Rhodomonas, Chlamydomonas, and Coelastrum), LimC strains grew on all sources, while a PnecB strain only grew on organic matter derived from Coelastrum (Horňák et al, 2017).…”