Biology subjects

Lujan, A.

Publications and source records attributed to Lujan, A..

4 recordsLinked to original sources

bioRxiv2022

Biphasic release propensity of mucin granules is supervised by TSPAN8

Agonist-mediated stimulated pathway of mucin and insulin release is biphasic in which a rapid fusion of pre-docked granules is followed by slow docking and fusion of granules from the reserve pool. The sustained neurotransmitter release also necessitates docking of vesicles from a reserve pool. We present here a surprising finding that plasma membrane-located tetraspanin-8 (Tspan-8) sequesters syntaxin-2 (Stx2) to control external agonist-dependent mucin release. Tspan-8 specifically affects fusion of granules in reserve during the second phase of stimulated mucin release. The Tspan-8 and Stx2 complex does not contain VAMP-8 and Munc18, which are required for fusion of mucin granules. We suggest that by sequestering Stx2, Tspan-8 prevents docking granules in the reserve pool. In the absence of Tspan-8, granules in reserve pool are free to dock to Stx2 and their fusion doubles the quantities of mucins secreted. Tspan-8 thus emerges as the long-sought component that controls biphasic mucin release. We suggest a similar mechanism likely controls biphasic insulin and sustained neurotransmitter release.

cell biology↗

bioRxiv2019

Interspecific social interactions shape public goods production in natural microbial communities

Evolution can occur over ecological timescales, suggesting a potentially important role for rapid evolution in shaping community trait distributions. However, evidence of concordant eco-evolutionary dynamics often comes from in vitro studies of highly simplified communities, and measures of ecological and evolutionary dynamics are rarely directly comparable. Here, we quantified how ecological species sorting and rapid evolution simultaneously shape community trait distributions by tracking within and between-species changes in a key trait in a complex bacterial community. We focused on the production of siderophores; bacteria use these costly secreted metabolites to scavenge poorly soluble iron and to detoxify environments polluted with toxic non-ferrous metals. We found that responses to copper-imposed selection within and between species were ultimately the same - intermediate siderophore levels were favored - and occurred over similar timescales. Despite being a social trait, this level of siderophore production was selected regardless of whether species evolved in isolation or in a community context. Our study suggests that evolutionary selection can play a pivotal role in shaping community trait distributions within natural, highly complex, bacterial communities. Furthermore, trait evolution may not always be qualitatively affected by interactions with other community members. SignificanceBacterial communities possess remarkable taxonomic and metabolic diversity and play a key role in nearly every biogeochemical process on Earth. Rapid evolution (occurring over ecological time scales) can in principle shape these processes, yet we have little understanding of its importance in natural communities. Here, we quantified how the production of metal-detoxifying siderophores is driven by species compositional changes and evolution in a compost community in response to copper stress. We found that siderophore production converged at intermediate levels, with evolutionary and ecological changes occurring at similar rates. Understanding how ecological and evolutionary processes contribute to shaping trait distributions will improve our ability to predict ecosystem responses to global change, and aid in the engineering of microbial consortia.

evolutionary biology↗

bioRxiv2019

Bacterial biodiversity drives the evolution of CRISPR-based phage resistance in Pseudomonas aeruginosa

Approximately half of all bacterial species encode CRISPR-Cas adaptive immune systems1, which provide immunological memory by inserting short DNA sequences from phage and other parasitic DNA elements into CRISPR loci on the host genome2. Whereas CRISPR loci evolve rapidly in natural environments3, bacterial species typically evolve phage resistance by the mutation or loss of phage receptors under laboratory conditions4,5. Here, we report how this discrepancy may in part be explained by differences in the biotic complexity of in vitro and natural environments6,7. Specifically, using the opportunistic pathogen Pseudomonas aeruginosa and its phage DMS3vir, we show that coexistence with other human pathogens amplifies the fitness trade-offs associated with phage receptor mutation, and therefore tips the balance in favour of CRISPR-based resistance evolution. We also demonstrate that this has important knock-on effects for P. aeruginosa virulence, which became attenuated only if the bacteria evolved surface-based resistance. Our data reveal that the biotic complexity of microbial communities in natural environments is an important driver of the evolution of CRISPR-Cas adaptive immunity, with key implications for bacterial fitness and virulence.

evolutionary biology↗

bioRxiv2017

Ecological selection of siderophore-producing microbial taxa in response to heavy metal contamination

Some microbial public goods can provide both individual and community-wide benefits, and are open to exploitation by non-producing species. One such example is the production of metal-detoxifying siderophores. Here, we investigate whether heavy metals select for increased siderophore production in natural microbial communities, or whether exploitation of this detoxifying effect reduces siderophore production. We show that the proportion of siderophore-producing taxa increases along a natural heavy metal gradient. A causal link between metal contamination and siderophore production was subsequently demonstrated in a microcosm experiment in compost, in which we observed changes in community composition towards taxa that produce relatively more siderophores following copper contamination. We confirmed the selective benefit of siderophores by showing that taxa producing large amount of siderophores suffered less growth inhibition in toxic copper. Our results suggest that ecological selection will favour siderophore-mediated decontamination, with important consequences for potential remediation strategies.\n\nAuthorshipEH, SOB, AL, DJH, EvV, AB conceived and designed the experiment. DJH provided new perspectives. EH, SOB, FB, AL collected the data. EH, FB, NT, DJH carried out the data analyses. EH & AB wrote the first draft of the manuscript, and all authors contributed substantially to revisions.\n\nData accessibilityUpon acceptance, data presented in the manuscript will be made available on Dryad.

ecology↗