Biology subjects

Griffin, A. S.

Publications and source records attributed to Griffin, A. S..

4 recordsLinked to original sources

bioRxiv2022

Core and accessory effectors of type VI secretion systems contribute differently to the intraspecific diversity of Pseudomonas aeruginosa

Bacteria use type VI secretion systems (T6SSs) to deliver effector proteins into other cells or the extracellular space. Those effectors kill microbes1, manipulate eukaryotic cells2, and sequester nutrients3. Which T6SS-mediated functions are generalisable across bacteria of a species or are specific to particular strains is little known. Here, we use genomics to test for the intraspecific diversity of T6SS effectors in the opportunistic pathogen Pseudomonas aeruginosa. We found effectors that are omnipresent and conserved across strains acting as core effectors, while additional accessory effectors vary. In vitro and in vivo experiments demonstrate different roles of the two types of effectors in bacterial killing and virulence. Further, effectors compose various effector combinations. Within one local population of clinical isolates, we observed 36 combinations among 52 bacterial lineages. These findings show the distinct contribution of T6SS effectors to strain-level variation of a bacterial pathogen and might reveal conserved targets for novel antibiotics.

microbiology↗

bioRxiv2021

Parental control: ecology drives plasticity in parental response to offspring signals

Different bird species have completely different parent-offspring interactions. When food is plentiful, the chicks that are begging the loudest are fed the most. When food is scarce, bird species instead feed the largest offspring. While this variation could be due to parents responding to signalling differently based on food availability, it could equally be due to offspring adjusting their behaviour, or to variation in information availability. We tested between these competing explanations experimentally, by manipulating food availability in a population of wild great tits, Parus major, while standardising offspring behaviour and size. We found that when food was more plentiful, parents were: (1) more likely to preferentially feed the chicks that were begging the most; and (2) less likely to preferentially feed larger chicks. In addition, we consistently found these same patterns, in a meta-analysis across 57 bird species. Overall, our results suggest that parents have more control over food distribution than offspring do, and that they flexibly adjust how they respond to both offspring signals and cues of offspring quality in response to food availability. Consequently, depending upon environmental conditions, predictably different signalling systems are favoured.

animal behavior and cognition↗

bioRxiv2021

Long-term evolution of antibiotic persistence in P. aeruginosa lung infections

Pathogenic bacteria respond to antibiotic pressure with the evolution of resistance but survival can also depend on their ability to tolerate antibiotic treatment, known as persistence. While a variety of resistance mechanisms and underlying genetics are well characterised in vitro and in vivo, the evolution of persistence, and how it interacts with resistance in situ is less well understood. We assayed for persistence and resistance with three clinically relevant antibiotics: meropenem, ciprofloxacin and tobramycin, in isolates of Pseudomonas aeruginosa from chronic cystic fibrosis lung infections spanning up to forty years of evolution. We find evidence that persistence is under positive selection in the lung and that it can particularly act as an evolutionary stepping stone to resistance. However, this pattern is not universal and depends on the bacterial clone type and antibiotic used, indicating an important role for antibiotic mode of action.

evolutionary biology↗

bioRxiv2018

Privatisation rescues function following loss of cooperation

A single cheating mutant can lead to the invasion and eventual eradication of cooperation from a population. Consequently, cheat invasion is often considered as \"game over\" in empirical and theoretical studies of cooperator-cheat dynamics, especially when cooperation is necessary for fulfilling an essential function. But is cheat invasion necessarily \"game over\" in nature? By following a population of bacteria through loss of cooperation and beyond, we observed that individuals evolved to replace cooperation with a selfish, or \"private\" behaviour. Specifically, we show that when cheating caused the loss of cooperative iron acquisition in a collection of Pseudomonas aeruginosa isolates from cystic fibrosis patients, a private uptake system that only benefits the focal individual was upregulated. This observation highlights the importance of social dynamics of natural populations and emphasizes the potential impact of past social interaction on the evolution of private traits.

evolutionary biology↗