Bacteria may induce the secretion of mucin‐like proteins by the diatom Phaeodactylum tricornutum

Abstract

Benthic diatoms live in photoautotrophic/ heterotrophic biofilm communities embedded in a matrix of secreted extracellular polymeric substances. Closely associated bacteria influence their growth, aggregation, and secretion of exopolymers. We have studied a diatom/bacteria model community, in which a marine Roseobacter strain is able to grow with secreted diatom exopolymers as a sole source of carbon. The strain influences the aggregation of Phaeodactylum tricornutum by inducing a morphotypic transition from planktonic, fusiform cells to benthic, oval cells. Analysis of the extracellular soluble proteome of P. tricornutum in the presence and absence of bacteria revealed constitutively expressed newly identified proteins with mucin-like domains that appear to be typical for extracellular diatom proteins. In contrast to mucins, the proline-, serine-, threonine-rich (PST) domains in these proteins were also found in combination with protease-, glucosidase-and leucine-rich repeatdomains. Bioinformatic functional predictions indicate that several of these newly identified diatomspecific proteins may be involved in algal defense, intercellular signaling, and aggregation.

Mobilization and Cellular Distribution of Phosphate in the Diatom Phaeodactylum tricornutum

“…The response to P i limitation correlates with a specific transcriptional upregulation of genes coding for alkaline phosphatases that are necessary for phosphate acquisition from DOP. Additionally, P. tricornutum has been reported to secrete the alkaline phosphatase PhoA (Lin et al, 2013;Buhmann et al, 2016;Erdene-Ochir et al, 2019), as well as a phytase-like protein (Buhmann et al, 2016;Erdene-Ochir et al, 2019), into the culture medium. A phosphate-specific reprogramming can be identified by P i transporters as well, as evidenced by the transcriptional upregulation of sodium-dependent phosphate cotransporters, permeases, and hydrogen-phosphate cotransporters (Dyhrman et al, 2012;Yang et al, 2014;Cruz de Carvalho et al, 2016;Alipanah et al, 2018) in P i -depleted media.…”

Evidence of Interdomain Ammonium Cross-Feeding From Methylamine- and Glycine Betaine-Degrading Rhodobacteraceae to Diatoms as a Widespread Interaction in the Marine Phycosphere

“…A major reason why heterotrophic bacteria establish transient and permanent interactions with diatoms is that diatoms perform autotrophic CO 2 fixation, which causes them to exude dissolved organic carbon (DOC) ( Amin et al, 2012 ) made up of various carbohydrates ( Passow, 2002 ; Grossart et al, 2006 , 2007 ; Molino and Wetherbee, 2008 ; Agogué et al, 2014 ; Klein et al, 2014 ; Buhmann et al, 2016 ; Doghri et al, 2017 ) as well as free amino acids and proteins ( Gärdes et al, 2012 ; Paul et al, 2013 ; Amin et al, 2015 ; Durham et al, 2015 ; Stahl and Ullrich, 2016 ). In this DOC pool, heterotrophic bacteria also have access to compounds such as dimethylsulfoniopropionate (DMSP), dimethylsulfoxide, or taurine, which are produced and excreted by various phytoplankton species ( Archer et al, 2011 ; Amin et al, 2015 ; Durham et al, 2015 ; Bullock et al, 2017 ).…”

Impact of Dinophysis acuminata Feeding Mesodinium rubrum on Nutrient Dynamics and Bacterial Composition in a Microcosm

“…The role of algal–bacterial interactions during harmful algal bloom (HAB) has received attention in recent years [ 26 , 27 , 28 ]. The supply of dissolved organic substances through cell exudation or cell lysis is hypothesized to be a major interaction between phytoplankton and the associated bacterial community [ 24 , 25 , 29 ]. The influence of bacteria on the toxigenic properties of photosynthetic microalgae (mainly Alexandrium spp.…”