Biology subjects

Blain, S.

Publications and source records attributed to Blain, S..

6 recordsLinked to original sources

bioRxiv2026

Dose-dependent transcriptional responses of marine prokaryotes to Fe-rich colloids of glacial and non-glacial origin in the Kerguelen region (Southern Ocean)

The trace metal iron (Fe) plays a key role in regulating microbial carbon metabolism through complex processes. In ocean regions where Fe is potentially limiting, new Fe sources can significantly influence prokaryotic activity and growth, stimulating the microbially-mediated cycling of carbon. The accelerated melting of glaciers delivers large quantities of Fe-rich material to the ocean, but the bioavailability of the diverse glacial Fe species remains poorly understood. Here, we investigated the response of marine prokaryotes to Fe contained in the colloidal fraction (20 - 200 nm size fraction) originating from the Cook Ice Cap on Kerguelen Island (Southern Ocean). We assessed growth and gene transcriptional responses to dose-additions of Fe-rich colloids from two sources, glacial meltwater and a non-glacial origin. The two colloid types resulted both in dose-dependent, but contrasting growth responses. While non-glacial colloids stimulated prokaryotic growth, the opposite pattern was observed with glacial colloids. The transcriptional profiles revealed an increasing trend in Fe-limitation, as evidenced by transcripts of the glyoxylate shunt, as a function of the addition of either colloid type. However, only non-glacial colloids induced a dose-dependent increase in transcripts of aromatic compound degradation, suggesting that these Fe-rich colloids could also provide C. These results point to the key role of C regulating the prokaryotic growth in response to Fe-rich colloids. The clear trends in the expression of genes in response to dose addition allowed to map transcript abundances to nutritional stress and specific metabolic pathways. Dose additions of limiting nutrients in incubation experiments induce quantitative transcriptional responses, thereby offering insights to the nutritional status of prokaryotes and to the mechanisms leading to Fe and C co-limitation.

microbiology↗

bioRxiv2026

TonB-dependent Transporters of Fe-petrobactin in Marinobacter nauticus and Southern Ocean bacteria

TonB-dependent transporters (TBDTs) play a central role in siderophore-mediated iron acquisition in the marine environment. However, assigning substrate specificity to TBDTs remains a major bottleneck in understanding the ecological and mechanistic roles of siderophore production and uptake. Here, we identify in Marinobacter nauticus two TBDTs, OptA and OptB, that share low sequence identity yet both mediate Fe-petrobactin uptake. Despite this functional overlap, they underlie distinct regulatory mechanisms, suggesting differential utilization under specific environmental conditions. Phylogenetic analyses indicate that OptA likely co-evolved with the petrobactin biosynthetic gene cluster, whereas OptB appears to have followed a distinct evolutionary trajectory, acquiring the capacity to import petrobactin as a xenosiderophore. Using resuscitated communities from the Southern Ocean, we further show that Fe-petrobactin stimulated prokaryotic growth. Based on amino acid similarity, we identified OptB-like transporters encoded in metagenomes and MAGs and show that taxa harbouring these transporters, such as Pseudoaltermonas, respond specifically to Fe-petrobactin addition. OptB-like transporters were also detected in environmental metagenomes from the Southern Ocean, whereas the petrobactin biosynthetic gene clusters were not, indicating that petrobactin primarily functions as a xenosiderophore in natural communities.

microbiology↗

bioRxiv2025

Species interactions, divergence, and the rapid evolution of ecological sexual dimorphism in threespine sticklebacks

Variation in ecological sexual dimorphism (ESD), defined as differences between the sexes in ecologically-relevant traits, is a common feature of adaptive radiation, yet its causes remain unclear. Competition between the sexes for alternative resources can promote evolution of ESD when interspecific competition is reduced (competition hypothesis). Alternatively, sex-specific selection on ecological traits might weaken under strong directional selection in new environments (divergence hypothesis). We tested these hypotheses via their expected evolutionary outcomes in threespine stickleback populations from southwestern Canada. We found striking among-population variation in magnitude of ESD. Consistent with the divergence hypothesis, dimorphism along the main axis of body shape variation was reduced in recently derived freshwater populations compared to their contemporary marine ancestor. However, dimorphism only weakly declined with increasing phenotypic divergence. Average dimorphism along major freshwater body shape axes was similar between solitary populations and those coexisting with a competing species, contrary to the competition hypothesis. Instead, sympatry with a Benthic ecotype led to increased sexual size dimorphism in Limnetics, and total shape dimorphism was elevated in the sympatric stickleback species compared with solitary populations. In contrast to the mechanisms considered in existing theory, interactions in sympatry might produce elevated ESD by generating novel sex-specific selection pressures.

evolutionary biology↗

bioRxiv2023

Tagging of water masses with covariance of trace metals and prokaryotic taxa in the Southern Ocean

Marine microbes are strongly interrelated to trace metals in the ocean. How the availability of trace metals selects for prokaryotic taxa and the potential feedbacks of microbial processes on the trace metal distribution in the ocean remains poorly understood. We investigate here the potential reciprocal links between diverse prokaryotic taxa and iron (Fe), manganese (Mn), copper (Cu), Nickel (Ni) as well as apparent oxygen utilization (AOU) across 12 well-defined water masses in the Southern Indian Ocean (SWINGS-South West Indian Ocean GEOTRACES GS02 Section cruise). Applying Partial Least Square Regression (PLSR) analysis we show that the water masses are associated with particular latent vectors that are a combination of the spatial distribution of prokaryotic taxa, trace elements and AOU. This approach provides novel insights on the potential interactions between prokaryotic taxa and trace metals in relation to organic matter remineralization in distinct water masses of the ocean.

microbiology↗

bioRxiv2019

Decreased alertness reconfigures cognitive control networks

Humans remarkable capacity to flexibly adapt their behaviour based on rapid situational changes is termed cognitive control. Intuitively, cognitive control is thought to be affected by the state of alertness, for example, when drowsy we feel less capable of adequately implementing effortful cognitive tasks. Although scientific investigations have focused on the effects of sleep deprivation and circadian time, little is known about how natural daily fluctuations in alertness in the regular awake state affect cognitive control. Here we combined a conflict task in the auditory domain with EEG neurodynamics to test how neural and behavioural markers of conflict processing are affected by fluctuations in alertness. Using a novel computational method, we segregated alert and drowsy trials from two testing sessions and observed that, although participants (both sexes) were generally sluggish, the typical Conflict Effect reflected in slower responses to conflicting information compared to non-conflicting information was still intact, as well as the moderating effect of previous conflict (Conflict Adaptation). However, the typical neural markers of cognitive control-local midfrontal-theta band power changes-that participants show during full alertness were no longer noticeable when alertness decreased. Instead, when drowsy, we found an increase in long-range information sharing (connectivity) between brain regions in the same frequency band. These results show the resilience of the human cognitive control system when affected by internal fluctuations of alertness, and suggest neural compensatory mechanisms at play in response to physiological pressure during diminished alertness. Significance StatementThe normal variability in alertness we experience in daily tasks is rarely taking into account in cognitive neuroscience. Here we studied neurobehavioral dynamics of cognitive control with decreasing alertness. We used the classic Simon Task where participants hear the word "left" or "right" in the right or left ear, eliciting slower responses when the word and the side are incongruent - the conflict effect. Participants performed the task both while fully awake and while getting drowsy, allowing for the characterisation of alertness modulating cognitive control. The changes in the neural signatures of conflict from local theta oscillations to a long-distance distributed theta network suggests a reconfiguration of the underlying neural processes subserving cognitive control when affected by alertness fluctuations.

neuroscience↗

bioRxiv2018

Prosody perception in children: studying individual differences with novel brain and behavioral approaches

A sizeable literature has shown that perception of prosodic elements bolsters speech comprehension across developmental stages; recent work also suggests that variance in musical aptitude predicts individual differences in prosody perception in adults. The current study investigates brain and behavioral methods of assessing prosody perception and tests the relationship with musical rhythm perception in 35 school-aged children (age range: 5;5 to 8;0 years, M = 6;7 years, SD = 10 months; 18 females). We applied stimulus reconstruction, a technique for analyzing EEG data by fitting a temporal response function that maps the neural response back to the sensory stimulus. In doing so, we obtain a measure of neural encoding of the speech envelope in passive listening to continuous narratives. We also present a behavioral prosody assessment that requires holistic judgments of filtered speech. The results from these typically developing children revealed that individual differences in stimulus reconstruction in the delta band, indexing neural synchrony to the speech envelope, are significantly related to individual differences in behavioral measurement of prosody perception. In addition, both of these measures are moderately to strongly correlated with musical rhythm perception skills. Results support a domain-general mechanism for cognitive processing of speech and music. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=150 SRC="FIGDIR/small/281998v1_ufig1.gif" ALT="Figure 1"> View larger version (68K): org.highwire.dtl.DTLVardef@7a4ca2org.highwire.dtl.DTLVardef@13d41c6org.highwire.dtl.DTLVardef@a9652borg.highwire.dtl.DTLVardef@130eb6a_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗