Different types of gut bacteria; yoghurt; diet, gut, weight and bacteria; inflammation and weight gain; salmonellae in eggs and chicken meat; Helicobacter Pylori; Toxoplasmata Gondii


- Best known family of gut bacteria, they love to feed on meat products

- Often they are the dominant population in the gut

- Carbohydrate breakdown experts, they have many genes for that purpose

- They can extract a lot of energy from food

- They produce a lot of biotin = vitamin B7 and vitamin H


- The opposite of bacteroides: there are more present in the vegetarian gut

- They have a long flagellum and travel to find useful proteins

- Produce sulphur compounds as a byproduct

- Other bacteria, desulphovironales take up the suphur

- They produce vitamin B1, which is required by our nerves to insulate them in fat. B1 deficiency causes muscle tremors and forgetfulness. Low levels of deficiency cause irritability, frequent headaches, concentration problems, high levels of deficiency cause beriberi: muscle atrophy and inability to walk in their sufferers.


- Feeds on plant cell walls

- Produces haem, needed for blood

Cows keep their bacteria in the beginning of their digestive tract. In this way they can:

1) Break down complex carbohydrates for them

2) They are themselves a rich source of protein: when they die they fall down the digestive tract and become themselves a source of food

In humans bacteria are too far down to provide any food, so they are passed out indigested.

Rodents have them as far down their digestive tract as us, so they don't digest bacteria. This is why they eat their own faeces: to not waste the bacterial protein that was excreted.

Yoghurt is pre-bacterially digested milk. The lactose is broken down and transformed into lactic acid: making ti both sweeter and sourer than milk. Lactic acid can either be dextrorotatory (left turning) or levorotatory (right turning). It is better to buy milk with dextrorotatory lactic acid for the human digestive system.

Diet, gut bacteria, weight

Fat mice fed the same diet as skinner mice secreted less indigestible calories: their gut bacteria fed them more.

Bacteria are capable of producing different fatty acids out of indigestible carbohydrates.

Vegetable-loving bacteria tend to produce fatty acids that feed the gut and the liver, and are therefore essential.

Other bacteria produce fatty acids that feed the rest of the body: so if you eat a banana vs a chocolate with the same amount of calories, the banana is less likely to make you fat since it will only feed the liver and gut as oppose to the whole body (very simplified summary considering only one aspect of digestion)

Obese people have less diversity in their gut flora: mainly groups of carbohydrate-loving bacteria prevail.

Inflammation causes weight gain

Metabolism problems: obesity, diabetes, high blood lipid levels usually come with increased levels of infection markers in the blood too.

A sub-clinical infection: the markers are there but they are not high enough to be detected or treated

Usually, the bacteria are located on the mucous membrane, and are not in contact with the gut bacteria. But when there are too many bacteria, or when the host eats an overly-fatty diet, too many bacteria walk into the bloodstream - this causes the body to slip into infection mode.

Bacterial signalling substances can also latch onto other organs, they can lock onto the liver or fatty tissue, and encourage the deposition of more fat.

They can also hinder thyroid function, thyroid hormone production, and slow the rate of fat burning.

Sub-clinical infection causes weight gain, hormonal imbalances, too much oestrogen production, too little vitamin D.

Bacteria can affect their host's appetite

We chose our food based on what we feel like eating at any given moment, and we stop eating when we feel satiated.

Bacteria can influence both of these conditions.

Bacteria needs to send signals to the brain to do this:

It produces Tyrosine and Tryptophan, amino acids needed for dopamine and serotonin production. So, in theory, the bacteria reward us when we send them food. It makes us feel good, and crave more food to bring about the same pleasure.

How does salmonellae get to eggs?

Salmonellae is a common gut dweller of African lizards. Cheap chicken feed comes from Africa, sometimes lizards or tortoises have excreted it in the feed, and when the feed gets eaten, it multiplies in the chickens and gets excreted by them too.

Chickens have one hole for both faeces and for eggs, so the shells get salmonella which gets transferred to the egg itself if the egg or the hands touch the outside of the shell.

How does salmonellae get into chicken meat?

After being slaughtered and beheaded, chickens are put into large baths, where one batch of infected chickens can infect them all.

The bacteria are then frozen with the chickens.

Usually the salmonellae gets transferred to other things during the thawing process of the chicken on the sink or other surfaces, and this is the main way it can infect humans.

10minutes of cooking at 75degrees celsius is enough to kill almost all salmonellae, so rarely is the method of cooking that which is the problem.

Helicobacter Pylori poets itself from the acids stomach with these mechanisms:

1) Byproducts of its metabolism are very alkaline so they neutralise any acid in their immediate vicinity

2) It burrows itself beneath the mucous membrane that protects the stomach from digesting itself.

There it injects substances into the cells which are eventually fatal to the stomach cells. So if the HP does not have the injecting gene, they cause less damage to the host.

3) By getting under the mucous membrane, HP damages it, so our stomach acids end up digesting parts of our stomach too - ulcers.

Sulphurophane blocked the enzyme that HP uses to neutralise gastric acid.

If too many stomach cells are destroyed, too many new ones are made to try and replace them, this can cause cancer.

They can also produce a neurotoxin, which in turn causes trembling hands, facial paralysis, motor problems.

Interestingly, people who have HP also have lower risk of dying of lung cancer, about a half chance.

HP also provides protection against childhood asthma. The theory for this is that the bacterium teaches the immune system to "stay cool":

It causes large numbers of T-cells to be produced when it latches onto our stomach cells.

T-cells calm down the immune response, so they also are less aggressive towards pollen and other allergens.

Toxoplasmata Gondii

Tiny, one celled organisms with very complex genetic information.

They reproduce in the guts of cats, which are their definitive hosts - which means that they are only able to reproduce there.

A cat can only get toxoplasmata once in it's lifetime, and it is a danger only during that initial time of infection: this is because when the toxoplasmata are found in the cats faeces, they mature in the litter for about two days, and then are ready to infect a host. They can stay in a human or other mammal for up to five years trying to find a definite host.

First symptoms are mild-flu-like.

But more importantly, it alters behaviour:

Infected rats have a decreased aversion to cat urine, an evolutionary adaptation to increase the parasite's reproductive success by getting the rodent to the cat. It happens through epigenetic remodelling of neurons which govern associated behaviours.

In people: the risk of being involved in a car accident is higher amount toxoplasmata carriers, especially in the early stages of infection.

Infected human men like cat urine smell more, and infected human women like it less.

How does it work?

When infected, the immune system activates the IDO enzyme to protect us from these parasites.

IDO breaks down a substance that the invaders like to eat, forcing them into a dormant state.

But IDO is also a substance needed to produce serotonin.

So less serotonin affects our mood negatively.

Also, the serotonin precursors that are now unused can dock onto brain receptors, causing lethargy. These are the same receptors for painkillers: causing indifference and sedation.

The amygdala is the part of the brain associated with fear:

Fibres run straight from the eyes to the amygdala, so even if the visual cortex is damaged and you cannot process visual information consciously, you can still get scared from a spider in your field of vision = blindsight.

If the amygdala gets damaged, a person may become fearless.

Toxoplasmata hibernate in muscles and in the brain: in the amygdala, the olfactory centre, the prefrontal cortex:

1) the rat can become more fearless

2) The rate does not dislike cat urine smell

3) it an weaken mechanisms that suppress self-destructive behaviour and decision-making

Toxoplasmata posses genes that influence the production of dopamine in the brain too.

Dopamine is over-abundant in schizophrenics.

The proportion of toxoplasmata carriers is twice as high in schizophrenics as in the the non-schizophrenic population..

Toxoplasmata is especially dangerous to pregnant women, who shouldn't touch or dispose of cat litter, and whose cat litter should be changed daily by someone else:

1) wash fresh fruits and vegetables well before eating

2) shovel cat litter daily

3) cook chicken well

4) stay away from kittens who have a higher risk of carrying toxoplasmata