Predation is one of the most prevalent and ancient forms of antagonistic interaction which pervades all ecosystems at all levels of biological organization. Studies with higher eukaryotes have demonstrated the significance of predator-prey interactions in speciation events, evolution of virulence, pathogenesis, emergence of diversity, cooperation, multiple levels of selection, and many more important events during the course of evolution of life on our planet. However, unlike the historical interest in studying predator-prey interactions among higher eukaryotes, the importance of microbial predator-prey interactions has been recognized relatively recently. We study bacterial predator-prey interactions in natural populations of bacteria, using evolution in test-tube approach.
We use M. xanthus as a model organism to study bacterial predation. M. xanthus is a predatory bacterium that kills and eats other microbes by secreting antimicrobial compounds and forms spore-filled multicellular fruiting bodies upon starvation. M. xanthus predation is mediated by contact-dependent as well as contact-independent mechanisms such as toxins, antibiotics, lytic enzymes, and secretion systems.
Specifically, we study the influence of translational and transcriptional errors, genetic diversity, environmental fluctuations, complex life-cycle, and ecological conditions on the evolution of mechanisms of bacterial predation. Please contact Samay or lab members if you want to know about our research.
Primary Areas of Interest
We use Myxococcus xanthus as a model organism to study the evolution of predation, and the influence of a complex life-cycle on the evolution of cooperation and development. M. xanthus belongs to the order Myxococcales, and are part of a group of bacteria commonly known as myxobacteria. Similar to its siblings, M. xanthus exhibits many fascinating collective behaviours and group living mechanisms.
For example, upon starvation, M. xanthus forms spore-filled multicellular fruiting bodies. The coordination of thousands of cells to form three-dimensional fruiting-body structures, in which only a minority will survive, is controlled by multiple contact-dependent and contact-independent signalling mechanisms.
M. xanthus are prolific hunters of many microbes, both prokaryotic and eukaryotic. M. xanthus predation involves cooperative foraging coupled with contact-dependent and contact-independent mechanisms of killing their prey. Because predation involves multiple M. xanthus cells, the group hunting strategy by M. xanthus is also known as wolfpack predation.
First reports of evolution experiments (by William Dallinger between 1880-1886) using microbes came soon after Darwin’s masterpiece “on the origin of species” (1859). Over the years microbial experimental evolution has become an important research tool.
Driven by precise questions, lab evolution experiments typically involve serial transfer of organisms (in our case microorganisms) under well-defined abiotic and biotic conditions. Bacteria are ideal model systems to perform such experiments because of their genetic tractability, possibility to maintain large population sizes, small generation times, and revivable ancestors.
In the past, microbial evolution experiments have resulted in the identification of some of the least expected outcomes. For example, the evolution of citrate utilisation by E.coli, identification of small regulatory RNA molecule in M. xanthus, and many more.
PREDATION AND ANTIMICROBIAL MECHANISMS
Microbes are fascinatingly social. They exist in complex communities, where both their ecological roles and evolutionary trajectories are largely dictated by their interaction with other members of the community. Within these communities, microorganisms are constantly competing in an evolutionary arms race and the production and secretion of antibiotics are one of the primary ammunition used during microbial warfare. Importantly, antibiotic resistance is one of the leading threats to health and healthcare systems globally. However, though the de-novo evolution of resistance driven by exposure to sub-inhibitory concentrations of antibiotics is studied extensively, the influence of microbial warfare on antibiotic resistance remains relatively less explored. In our lab, we study the influence of prey-predator interaction on antibiotic resistance: both on an ecological scale as well as along an evolutionary time scale.
M. xanthus lifecycle
EVOLUTION AND LIFE CYCLE
Myxococcus xanthus has a complex life cycle with distinct life-history stages, which involve different degrees of sociality. Therefore, we are interested in studying the evolutionary processes involved in the evolution of life cycles of organisms such as M. xanthus. Currently, we are keen on the identification of the trade-offs between distinct life-history traits, the importance of population sizes on the evolution of complex life cycles with aggregative multicellularity, and the evolution of developmental traits in M. xanthus populations that emerged in laboratory evolution experiments.
Microbes exist in complex communities, in which their ecological roles and evolutionary trajectories are largely dictated by their interaction with other members of the community. Within these communities, microorganisms are constantly competing in an evolutionary arms race. The production and secretion of antibiotics is one of the important mechanisms used in microbial warfare strategies. Hence, it is likely that bacteria in nature use antibiotic resistance as a survival strategy in natural microbial communities. However, though the de-novo evolution of resistance driven by exposure to sub-inhibitory concentrations of antibiotics is studied extensively, the influence of microbial warfare on antibiotic resistance remains relatively less explored. In our lab, we study the influence of prey-predator interaction on antibiotic resistance: both on an ecological scale as well as along an evolutionary time scale.