definearth

Horizontal gene transfer was first discovered in 1928, but like many topics in the science realm there is still so much to learn about it. A talk I attended recently highlighted the fact that up to 10% of bacterial DNA wasn’t originally their DNA. Bacteria have the ability to “shop around” for bacteria, adding genes that spark joy to their initial DNA. After a few generations the unuseful DNA tends to get deleted, but certain bacteria may choose to keep it. This is one way that bacteria “evolve” even though they don’t undergo meiosis (combination of an egg & sperm).

Things Marie Kondo and Bacteria Have in Common

• Small
• They are very much alive!
• Get rid of things that don’t spark joy

Bacterial DNA can be altered by horizontal gene transfer (HGT) or by accidents in gene expression. In order for HGT to take place, there has to be: (1) cell-to-cell contact (conjugation), (2) transfer between bacteria through a viral bacteriophage, or (3) uptake of naked DNA in the environment (transformation).

Naked DNA gets into our environment when cells burst. Cell bursting, or apoptosis, happens after death. So imagine a plant dies, shrivels, and leaves fragments of naked DNA in the soil it once inhabited. Soil bacteria such as rhizobia can come along and hoard pieces of this DNA in the hopes that it will one day be useful. The soybean root in the photo above has been infected by soil rhizobia. Rhizobia are beneficial to plants because they help it uptake Nitrogen.

Bacteria in Clouds

A short study published in Science revealed that more than 69% of fallen snow contained bacteria as cloud condensation nuclei which helped water vapor in the atmosphere to form into droplets, as opposed to the usual suspect of dust. Bacteria in fallen snow typically originates from plants as plant pathogens. An example of a plant pathogen is Ralstonia solanacearum. This bacterium infects the xylem and makes the plant wilt. Xylem refers to the hollow, woody part of the plant made of dead cells that transports water.

I’ve always attributed the smell of rain to damp earth and worms. I’ve even questioned if the smell came from the rain itself. The truth is, rain gets its smell from a soil bacteria called Actinomycetes. And that’s my last fun fact for today! I hope you enjoyed this post. Do you like the smell of rain? Feel the need to clean your yoga mat now that you’ve learned about bacteria? Reply in the comments! Sincerely, Jess 🙂