Table 1. Examples of putative dual-use traits related to pathogenic and environmental fitness of human pathogens.

Organism	Trait or Gene	Role in Pathogenic Fitness	Role in Environmental Fitness	Reference
Vibrio cholera	Toxin co-regulated pilus	Virulence factor in humans	Biofilm formation on chitin	[59],[60]
Legionella pneumophila	Eukaryotic-like proteins that mimic cellular functions of eukaryotic proteins; type II and type IV secretion systems, surface proteins involved in attachment, secreted effectors	Virulence factors in macrophages	Parasitism and multiplication in protozoa	[61]
Burkholderia cenocepacia	Quorum-sensing regulatory system	Regulation of virulence factors implicated in “cepacia syndrome”	Regulation of factors involved in nematode killing	[62]
Yersinia pestis	Extracellular polysaccharide production linked to the action of heme storage gene (hms) products	Transmission to the human host and protection from the action of leukocytes	Colonization of flea esophagus via biofilm formation	[63]
Cryptococcus neoformans, Alternaria fumigatus	Melanins	Protects microbial cells against phagocytosis	Protection against oxidation	[24]
Alternaria flavus, Histoplasma capsulatum, Aspergillus fumigatus, A. nidulans and numerous bacteria	Siderophores	Virulence factor in humans	Sequestering iron in the environment	[21]–[23]
Pseudomonas aeruginosa and Stenotrophomonas maltophilia	Efflux pumps	Intrinsic multidrug resistance	Exclusion of lipophilic toxic compounds from cells	[10],[64],[65]
Acinetobacter baummannii	Efflux pumps, genetic promiscuity, exopolysaccharides and biofilm formation, siderophore-like compounds	Multidrug resistance, attachement, stimulation of host inflammation, virulence factor in humans	Exclusion of toxic compounds from cells, resistance to desiccation, sequestering of iron	[66]