As ketamine’s demonstrable therapeutic applications have become ever more popular, earlier research lauding its potential as an antimicrobial and antiparasitic agent has quietly reemerged. The last several years have seen a palpable enthusiasm regarding ketamine’s potential utility in the treatment of depression, anxiety, and related maladies. This research culminates at present with the work of McInnes and colleagues, sponsored by the healthcare technology company Osmind. This study, from the Journal of Affective Disorders, is the largest outcomes analysis of Ketamine Infusion Therapy (KIT) to-date, and reiterated ketamine’s ability to elicit a robust and durable antidepressant response. Beneath the attention ketamine’s therapeutic effects have received, a more obscure discovery has been made: a 2020 study in Parasites & Vectors found that the fungus Pochonia chlamydosporia is a natural source of ketamine. The isolated compounds evidenced nematicidal activity (the ability to kill nematodes, a variety of predominantly parasitic worms). Upon separation and purification of the isolates liberated from P. chlamydosporia, ketamine was revealed as a major constituent. In addition to its anthelmintic properties (the ability to kill worms more generally), ketamine also has apparent antimicrobial effects. In 2018, work published in Pathogens and Disease concluded that ketamine slowed the growth and spatial expansion of infectious microbes, and even speculated on how the antibiotic activity may be mediated. These properties illustrate similarities between fungal, bacterial, and human biology that can be exploited for the development of new antibiotic and anthelmintic drugs. They also show more fundamentally that ketamine acts not only in the brain, but on microbial communities.