Table 1.

Social traits exhibited by bacteria compared with examples from vertebrates and invertebrates.

cooperative behaviour	group-derived benefits	microbe examples	higher organism comparisons
chemical communication (quorum sensing)	coordinated population behaviour	Vibrio fischeri, Pseudomonas aeruginosa, Staphylococcus aureus, etc.	pheromone production in many social animals
biofilm formation	protection from adverse environmental conditions	many species of bacteria	Burrows, nests, hives, cities
nitrogen fixation: mutualistic behaviour	nutrients and niche protection in nodules	Rhizobium spp. with legume plants	yucca plant and yucca moth
foraging/hunting: nutrient acquisition	enhanced growth and colonization sometimes in specialized niches	siderophore production for iron acquisition in many bacteria	wolves, lions, humans
autolysis (suicide)	provides nutrients and DNA for biofilm development	P. aeruginosa	apoptosis in eukaryotic cells
motility (swarming)	coordinated motility to a nutrient source	Yersinia spp., Myxococcus xanthus, P. aeruginosa	ants, termites
antibiotic resistance	production of extracellular enzymes (e.g. β-lactamase) to break down antimicrobials	Escherichia coli, Klebsiella spp.	group defence, antipredator vigilance
immune modulation	modulation of immune response to facilitate survival within the host	P. aeruginosa, Porphyromonas gingivalis, Helicobacter pylori	helminth parasites