--- title: The microscopic world: bacteria, good and bad — a lesson of Mova's school · trees and pragmatics description: «The microscopic world: bacteria, good and bad», a lesson of the biology course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: Bacteria are living things made of just one tiny cell, so small that hundreds could sit side by side across the full stop at --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/) [home](https://md.mova.elamur.ai/free/en/) / [corpora](https://md.mova.elamur.ai/free/en/corpora/) / [school](https://md.mova.elamur.ai/free/en/corpora/school/) / [Biology](https://md.mova.elamur.ai/free/en/corpora/school/biology/) / The microscopic world: bacteria, good… # The microscopic world: bacteria, good and bad Lesson 257 of the biology course of Mova's primary school: 16 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0). How Mova does on its tests: [the lesson at school](https://md.mova.elamur.ai/free/en/school-run/biology/257-the-microscopic-world-bacteria-good-and-bad/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/0/) — Bacteria are living things made of just one tiny cell, so small that hundreds could sit side by side across the full stop at the end of this sentence; they live everywhere, from deep rocks and clouds to Antarctic ice and your own tummy. - [1](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/1/) — Cartoons draw germs as angry green monsters, but most bacteria are harmless or even helpful, and only a small number make people ill. - [2](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/2/) — The yoghurt in your fridge was made by bacteria that turned milk sugar into acid, and the bacteria in your gut help digest your dinner and make vitamins for you. - [4](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/4/) — Bacteria multiply by splitting in two, as often as every 20 minutes, which is why milk left out on a warm day goes sour so fast and why food lasts longer in the cold fridge. - [5](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/5/) — Yoghurt is made by bacteria that turn milk sugar into acid, which thickens the milk and makes it sour; bacteria also help make cheese, pickles, sauerkraut and sourdough bread. - [7](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/7/) — Bacteria can become resistant to antibiotics if the medicines are overused, which is why doctors do not give them for colds. - [8](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/8/) — In 1928 Alexander Fleming noticed that a mould on a dish had killed the bacteria around it, which led to penicillin, a medicine that has saved many millions of lives. - [9](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/9/) — About as many bacteria live in and on your body as there are cells of your own, mostly in the gut, and together they weigh about 200 grams. - [10](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/10/) — Gut bacteria help digest food, make some vitamins and protect against harmful germs. - [11](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/11/) — Soap breaks up the greasy layer on germs and lifts them off the skin; washing for about 20 seconds, between fingers and under nails, removes most of them. - [12](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/12/) — In 1847 the doctor Ignaz Semmelweis found that handwashing by doctors saved mothers' lives, but many other doctors laughed at him, because nobody yet knew that germs spread illness. - [13](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/13/) — In good conditions a bacterium can split in two every 20 minutes, so one can become millions in a few hours; a fridge slows bacteria down but does not kill them. - [14](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/14/) — The rainbow colours of hot springs in Yellowstone come from different bacteria living at different temperatures, some in water near boiling. - [16](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/16/) — Bacteria and fungi are decomposers: in compost and in soil they break down peelings, dead leaves and dead animals, give off heat as they work, and return nutrients to the soil; a big heap can reach about 60 degrees in the middle. - [17](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/17/) — Billions of years ago, cyanobacteria made the first oxygen in the air by photosynthesis, and the rocks they built, called stromatolites, still grow in Shark Bay, Australia. - [18](https://md.mova.elamur.ai/free/en/corpora/school/biology/257-the-microscopic-world-bacteria-good-and-bad/18/) — Some scientists think meeting many harmless germs outdoors and with animals trains a child's immune system, but this is still studied and never means skipping handwashing before eating or after the toilet. - ← previous: [The microscopic world: cells, the building blocks of life](https://md.mova.elamur.ai/free/en/corpora/school/biology/256-the-microscopic-world-cells-the-building-blocks-of-life/) - next →: [The microscopic world: viruses and vaccines](https://md.mova.elamur.ai/free/en/corpora/school/biology/258-the-microscopic-world-viruses-and-vaccines/) - ↑ back to [Biology](https://md.mova.elamur.ai/free/en/corpora/school/biology/)