Beer yeast was "found" by Louis Pasteur in the late 19th century and N. Hjelte Claussen managed to isolate some of the strains.
It's important to consider that when fermenting beer, you will get a more pure and clean fermentation if you can ferment at a low temperature. At high temperatures, you will get esters and phenols in abundance, i.e. unwanted flavours. We have listed the best temperature range for each type of yeast for your convenience.
Beer yeast comes in many different strains and they are often classified after terms such as "flockulation", "attenuation" and what temperature it is designed to work at.
Flockulation:How well and compact the yeast cells form a bottom sediment once the fermentation is over. Belgian strains have low flockulation which will result in a cloudy beer. English strains have often high flockulation so you can produce a clear beer without filtering or clearing agents.
Attenuation:To put it simply, it is how much sugar (or fementable matter) the yeast can consume before it goes dormant. A beer made from yeast with high attenuation will be drier than one fermented with a low attending yeast strain.