Bacteria–algae association in batch cultures of phytoplankton from a tropical reservoir: the significance of algal carbohydrates

Abstract

1. The dissolved organic matter, especially carbohydrates, released by phytoplanktonic organisms may be ecologically important, through its influence on carbon cycling and microbial diversity. Here axenic cultures of three phytoplanktonic species, Cryptomonas tetrapyrenoidosa (Cryptophyceae), Staurastrum orbiculare (Zygnematophyceae) and Thalassiosira duostra (Bacillariophyceae), were inoculated with a microbial community from the same habitat in which the algae had been isolated (a tropical reservoir). Replicate cultures were not inoculated. 2. In both axenic and co-inoculated cultures, phytoplanktonic density and extracellular carbohydrate production were monitored microscopically and by high performance liquid chromatography with a pulse amperometric detector, respectively. Bacterial population density was also monitored by epifluorescence microscope in the microbial co-inoculated cultures. 3. Both bacterial and phytoplanktonic densities increased for 11 days in all cases. The use of extracellular carbohydrates by bacteria was also showed for all phytoplanktonic species. Of the three species of phytoplankton, only T. duostra had a faster population growth in the presence of bacteria, and reached a higher biomass than in axenic culture.

Morphological and physiological changes in Microcystis aeruginosa as a result of interactions with heterotrophic bacteria

“…However, bacteria populations increased when, or soon after, the phytoplankton biomass reached it maximum. Giroldo, Ortoland & Vieira (2007) also found that phytoplanktonic extracellular organic compounds, including carbohydrates, supported dense bacterial populations, even at very low concentrations. Dissolved EPS released from phytoplankton is a major component of dissolved organic carbon (DOC) in freshwater and is beneficial for bacterial growth (Sundh, 1992).…”

Spatio-temporal patterns of bacterioplankton production and community composition related to phytoplankton composition and protistan bacterivory in a dam reservoir

“…Sundh 1992, Giroldo et al 2007). Even so, it is not known which algal species are the major EPP producers, though tight species-specific algal-bacterial relationships have been suggested for naturally occurring bacterial-algal consortia (Lindström 2001, Grossart et al 2005, Murray et al 2007.…”

Bacterial degradation of dissolved organic matter released by Planktothrix agardhii (Cyanobacteria)

“…Although the high availability of phytoplankton-originated DOC it can still be accumulated during blooms of freshwater phytoplankton, creating a pool of residual DOC (Kragh and Søndergaard, 2004). Different compounds, like polysaccharides, might be more or less degradable by bacteria (Giroldo et al, 2007), requiring specific adaptations for its success and even the degradation itself might result in more refractory compounds (Bittar et al, 2015). However, this residual DOC still have a appreciable return to the pelagic food web via bacterial consumption (Coveney and Wetzel, 1989), although at a slower pace, and thus, assuming an considerable ecological role.…”

“…The quality and availability of compounds in these released DOM and the presence of specialists and generalists bacterial groups will influence the bacterial community composition during the degradation process (Allen et al, 2005;Davidson et al, 2007;Giroldo et al, 2007). Therefore, we focused on trying to estimate the fate of dissolved organic carbon and nitrogen released by axenic cultures of P. agardhii under bacterial degradation, and simultaneously determine the main bacterial OTUs (Operational taxonomic units) involved in the process.…”

“…It is responsible for the production of large quantities of particulate organic carbon (Kokociński et al, 2010), and also release large quantities of dissolved organic carbon (DOC) naturally by health cells (Dellamano-Oliveira et al, 2007). The dissolved organic matter (DOM) released by phytoplankton is a recognized source of high quality organic carbon for heterotrophic organisms, mainly bacterial populations (Giroldo et al, 2007;Sarmento and Gasol, 2012). In general, the DOM released by phytoplankton is swiftly consumed and remineralized by the bacterial community and the degradation process allows the reintroduction of compounds in the trophic net, reinstating their availability to higher trophic levels (Azam et al, 1994;Thomas, 1997), and thus, avoiding the loss of compounds, which could otherwise reach the bottom of the reservoir or be exported downstream.…”