Bacterial genes Bacterial statistics More of this about that Commentary

Salvador Luria, Max Delbrück genetics

Bacterial genes

• Luria and Delbrück’s experiments showed
• that Darwin’s natural selection applies to bacteria.
• Genetic mutations giving viral resistance are selected
• by environmental conditions and passed to descendants.
• Even though bacteria have no cell nucleus as we do,
• their life instructions are structured the same as ours.

Bacterial statistics

• The famous Luria-Delbrück experiment
• used statistics to make quantitative predictions
• about the inheritance of viral resistance in E. coli bacteria.
• Mutations conferring resistance occur randomly;
• resistance is not induced from bacterium to bacterium;
• nor does it occur as a response to the environment.

More of this about that

• Forty million bacterial cells live in each gram of soil;
• a million bacterial cells live in each milliliter of fresh water.
• Over thirty bacterial species hitch rides in the cuticle and gut
• of each cockroach, with fourteen million microbes on each
• and seven million in each of their fecal droppings.
• Lest, dear reader, you start to feel superior,
• your own body hosts thousands of bacterial types;
• up to a thousand species live in your gut,
• and ten times more bacteria than human cells live in your body.