Bacteria, Yeasts and Virus :

Bacteria, Yeasts and Virus are all around us and inside us and as an ever present life form are good to know as a way to harness their fermentation powers and to avoid pathogenic strains. I also mentioned viruses because some virus infect bacteria and for example in the case of the respiratory track help us fight bacteria, some viral therapy using bacteriophage or phages have been successfully used for almost a century in some eastern countries but have serious problems to fit inside the actual neo-liberasl market. We'll almost limit for now our analysis of these micro-organisms to the main points linked to fermentations :

Diverse facts about bacteria and Yeasts:

• Bacteria and yeasts communicate between each others quorum sensing, this could lead to strange effect in some batches, like a halt to the fermentation when conditions and strains are just fine! Could be some slow down message going through. By the way it's not impossible for these messages to go through the air, for example kefir production tend to slow down (personal observation) if an almost rotten kefir jar is sitting nearby.
• They eat most of the time except when a quorum signal tell them to slow down and also probably when splitting (mitosis).
• If they are well, they do not die, they just split.
• They do not have to sleep like we do, but some species have resting phases for example connected to quorum sensing or environmental factor, see Do microbes sleep ? or Bacterial circadian rhythms.
• Some have some sort of sexual activities called Bacterial conjugation, they can exchange genes with a sort of tube. It's with these sort of tools that microbes can become antibiotic resistant even if they haven't been exposed.
• They have incredible biochemical possibilities and can be harnessed to produce many different substances, the most notorious being alcohol and many different acids (lactic, acetic etc.)
• Lactic acid was coined with a milk related prefix because it was probably first observed in milk, but pure vegetable fermentation like sauerkraut are also named lactic fermentation because lactic acid is produced, but without any milk.
• Yeasts cells have a nucleus like our cells when bacteria don't.
• Bacteria are sensitive to "bacterial antibiotics" often simply named antibiotics
• Yeasts are sensitive to antifungal that tend to be more toxic for us because of the similarities our cells share with yeasts (mainly a nucleus).

Human centered categorization of micro-organisms :

• Symbiotic : they help us to produce diverse substances, like vitamin K
• Neutral often called Saprophyte : they just eat what's passing around but do not interfere negatively for example with toxic production.
• Pathogenic : aggressive micro-organisms producing toxic substances interfering with our health.

As far as we are concerned symbiotic and neutral micro-organisms just because being there offer a very interesting protection against pathogenic micro-organism because they are in competition with them for space and food! Some micro-organisms may even directly attack pathogenic strains, the most well known are their natural viral enemies in other words their natural bacteriophage and we probably have symmetrical situation with yeasts.

What about clostridium botulinum the nasty bacterium responsible of botulism ? This is a freaky micro organism, but most scoby have 4 huge advantages over it :

1. Acidic medium
2. Oxygen resistance
3. Fierce competition
4. No selection of heat resistant spore.

On the reverse a badly heated canned food (may be just boiled) containing meat has none of the above points and in fact selected heat resistant germs inside the perfect environment for clostridium botulinum to thrive and the botulinum toxin to pile up : no competition (all the others microbes got burned), plenty of food, a neutral PH and no oxygen! In other words a clostridium botulinum paradise!

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