Why are there pathogenic Mycobacterium species, that cause tuberculosis, leprosy, etc.? I found some articles about experiments where they infected amoebae with various Mycobacterium species including M. tuberculosis and thought the pathogenic species must have evolved from bacteria like these. Its known that some Mycobacterium species can act as parasites and/or endosymbionts with amoebae. I found this article later. TB and leprosy involve infection of macrophages.
https://en.wikipedia.org/wiki/Macrophage
Quote:
An interesting feature of many mycobacterial species is their ability to survive inside amoebae, leading to the classification of mycobacteria as ‘amoeba-resistant micro-organisms' (Greub & Raoult, 2004). The mechanisms used by macrophages and amoebae for phagocytosis, phagolysosome formation and digestion of intracellular bacteria are very similar (Allen & Dawidowicz, 1990a, b; Brown & Barker, 1999; Greub & Raoult, 2004; Winiecka-Krusnell & Linder, 2001). Reciprocally, the strategies employed by bacteria to escape destruction by macrophages or amoebae are also similar. This supports the theory that an evolutionary selection for survival in environmental protozoa has enabled intracellular pathogenic bacteria to develop the capacities necessary for survival in macrophages (Brown & Barker, 1999; Steinert et al., 1998; Winiecka-Krusnell & Linder, 2001). In this context, it is interesting that passage through amoebae can enhance the virulence of pathogenic intracellular bacteria and that there exists a correlation between the virulence of mycobacterial species and survival in amoebae (Cirillo et al., 1997).
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https://www.microbiologyresearch.org...mic1512403.pdf