# Kin recognition and outer membrane exchange regulate social interactions in myxobacteria

> **NIH NIH R01** · UNIVERSITY OF WYOMING · 2020 · $289,657

## Abstract

Abstract
A fundamentally important question in biology is how individual cells within multicellular
organisms cooperate to form tissues, organs and a complete organism. One approach to address
this complex question is to use simple model systems that exhibit many of the traits found in
tissues. Myxococcus xanthus is one such system where, for instance, in response to starvation
thousands of cells aggregate, move rhythmically and build fruiting bodies in which vegetative
cells differentiate into spores. In M. xanthus we discovered a novel platform that mediates social
interactions. This behavior involves kin recognition in which cells identify clonemates and
exchange outer membranes (OM) proteins and lipids. Recognition in outer membrane exchange
(OME) is mediated by a polymorphic cell surface receptor called TraA and its partner protein
TraB. Only cells that bear identical or very similar alleles of traA will recognize one another for
OME. Depending of conditions the exchange of OM content leads to beneficial or harmful
outcomes. In genetic models we showed that OME can result in cooperative repair of damaged
cells. Here, healthy cells replenish mutant cells with missing components that restores their
fitness. In other examples, OME leads to antagonisms when polymorphic toxins are transferred
and the recipient cells do not contain cognate immunity proteins. Although OME involves the
apparent transfer of hundreds of different cellular components with complex social
consequences, this system is amendable to powerful approaches that can be applied to bacterial
research. This proposal addresses three goals. In Aim 1 we will investigate OM fusion as the
mechanism for exchange by using microscopy, genetic and biochemical methods to define the
dynamic functions of TraA and TraB. Aim 2 will also use a combination of approaches to define
the molecular basis of TraA kin recognition and how it interacts with TraB. Aim 3 will investigate
a second pathway that allows toxins delivered by OME to enter the cytoplasm. Our preliminary
data suggests that this kin discrimination system impacts strain diversification and population
structures found in natural soil habitats. This hypothesis will be tested by genetic and
bioinformatic experiments. Last, the ability of OME to repair damage that is inflicted on stressed
cells will be tested. These studies will lead to a molecular understanding of the mechanisms of
kin recognition and OME, as well as a deeper insights into how a socially sophisticated bacterium
transitions from individuals into a cooperative multicellular tissue.

## Key facts

- **NIH application ID:** 9975187
- **Project number:** 5R01GM101449-09
- **Recipient organization:** UNIVERSITY OF WYOMING
- **Principal Investigator:** DANIEL WALL
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $289,657
- **Award type:** 5
- **Project period:** 2012-05-01 → 2022-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9975187

## Citation

> US National Institutes of Health, RePORTER application 9975187, Kin recognition and outer membrane exchange regulate social interactions in myxobacteria (5R01GM101449-09). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9975187. Licensed CC0.

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