Bacteria — Friends and Foes

BACTERIA are SINGLE-CELLED organisms without nuclei (prokaryotes). They are everywhere: soil, water, air, deep in rock, on your skin, in your gut, on every surface. There are estimated 10^30 bacteria on Earth — more than stars in the observable universe. Most are HARMLESS. Many are HELPFUL. A few are PATHOGENIC (disease-causing).

Helpful bacteria. GUT BACTERIA help digest food and produce vitamins. SOIL BACTERIA fix nitrogen plants need. CYANOBACTERIA in oceans produce much of Earth's oxygen. FERMENTATION bacteria make yogurt, cheese, kimchi, sauerkraut, sourdough. INDUSTRIAL bacteria produce insulin (genetically engineered E. coli), enzymes, biofuels. Some bacteria can clean up oil spills (bioremediation).

Pathogens. Some bacteria cause serious disease. STREPTOCOCCUS (strep throat). E. COLI (some strains cause food poisoning). SALMONELLA (food poisoning). MYCOBACTERIUM TUBERCULOSIS (TB — kills more than 1 million yearly). VIBRIO CHOLERAE (cholera). YERSINIA PESTIS (plague — killed 1/3 of Europe in the 1340s). Most bacterial infections respond to antibiotics. But resistance is growing. Vaccination prevents some bacterial diseases (TDaP, pneumococcal).

Bacteria are not just "germs." They are the most diverse and successful kingdom of life. Most are partners or neutral. Treating them as a category requires nuance.