Role of Bacteria in shaping behavior of genes

14/09/2011

Maneka Gandhi

(Bihar Times)Are you a worrier? Do you have violent mood swings?

Researchers studying behaviour and gene activity in mice have found that bacteria in the intestines appear to shape brain and personality development .

Hundreds of species of bacteria call the human gut their home. In fact our bodies are so little “human” inhabited as they are by worlds of bacteria, worms and other parasites. While scientists have known for years that these colonists influence our state of health by releasing toxins into our blood new studies say that gut bacteria can even mess with the mind, altering brain chemistry and changing mood and behaviour.

Research at the Genome Institute in Singapore found that gut microbes controlled the activity of a gene important to the production of serotonin, a key brain chemical. A study undertaken to assess behavioural differences between bacteria-free mice and mice with intact gut bacteria found differences in activity and anxiety levels. Bacteria-free mice were more daring and less anxious. Most mice tend to seek refuge in dark areas—but not the germ-free mice who roamed freely in open areas. When bacteria free pregnant mice were exposed to gut microbes, their children were less active and more anxious, showing the role of the bacteria in shaping behaviour.

Analysis of the chemistry in the brains of these mice found dozens of different activity levels in the genes between them specially with brain chemicals associated with anxiety, such as noradrenaline and dopamine. Researchers at McMaster University in Canada fed mice a broth containing a benign bacterium, Lactobacillus rhamnosuss . (Lactobacillus is the bacteria in curd) Mice whose diets were supplemented with L. rhamnosuss exhibited less fear. They explored narrow elevated walkways and wide-open spaces, which are scary to rodents, and they exhibited a smaller spike in stress hormone levels when put in water. None of these effects occurred in mice that ate no added bacteria. The antianxiety effects of L. rhamnosus disappeared when the researchers cut the vagus nerve before feeding the bacteria to mice. This nerve is the conduit of sensory information from the gut to the brain, and this experiment shows it must be intact for L. rhamnosus to have an effect on the brain - a clear indication of how the bacteria sent messages to the brain. What it means is that you can alter emotional states by regulating the bacteria.

How easy it would be to control mood disorders by simply feeding people curd. The most influential of all bacteria is Toxoplasma . In fact they could be the bosses of the world controlling your thought and actions ? Did you know that half of the world's human population, approximately three billion, are infected with Toxoplasma parasites. In France, for example, around 88% of the population are carriers. Germany, the Netherlands and Brazil have 68%, over 80% and 67% respectively. In Britain 22% are carriers. No studies done in India. Toxoplasma gondii is a common parasite found in the guts of cats; it sheds eggs that are picked up by rats and other animals eaten by cats. The bacteria reach a level of maturity in these animals. But it has to get back to the cat to mature and lay eggs. So Toxoplasma forms cysts in the brains of rats. If the rats die, the cats won’t eat dead bodies. The bacteria are so smart. It becomes a "good" parasite, leaving the rats perfectly healthy. But it subtly alters the minds of infected rats. Normal rats will avoid any area that has the smell of cat urine – in fact a whiff causes panic reactions in a rat. But Toxoplasma-ridden rats show no such reaction. They actually seek out the cat urine-marked areas again and again till they get killed by the cat and the bacteria can re-enter the cat’s body.

The parasite alters the mind and behaviour of the rat for its own benefit.If the parasite can alter rat behaviour, does it have any effect on humans? Researchers have noticed clear links between Toxoplasma and schizophrenia in human beings. Toxoplasma infection is associated with damage to brain cells called astrocytes. Schizophrenia is also associated with damage to astrocytes. Pregnant women with Toxoplasmosis are more likely to give birth to children who will develop schizophrenia. Human cells infected with Toxoplasma, will respond to drugs like haloperidol; the growth of the parasite stops. Haloperidol is an antipsychotic, used to treat schizophrenia. Rats given haloperidol to remove their infection reverted to their normal behaviour of avoiding cats. All studies have found that schizophrenics have elevated rates of Toxoplasma infection.

The parasite produces an enzyme with tyrosine hydroxylase and phenylalanine hydroxylase activity. This enzyme alters the production of dopamine, a neurotransmitter involved in mood, sociability, attention, motivation and sleep patterns. Schizophrenia has long been linked to dopamine dysfunction.

The Toxoplasma parasite infects all warm blooded animals, including humans, but the primary host is the cat family. Infection comes through:* Ingestion of raw or partly cooked meat or during hand-to-mouth contact after handling undercooked meat, or from using knives, utensils, or cutting boards contaminated by raw meat or fish. *Ingestion of contaminated cat faeces. However direct infection from handling cats is very rare.

*If the pregnant mother has the parasite , the unborn baby can get congenital toxoplasmosis. During the first few weeks the infection may cause a mild flu-like illness. Thereafter, the parasite rarely causes any symptoms in otherwise healthy adults. Most infants who are infected while in the womb have no symptoms at birth However, those with a weakened immune system may become seriously ill and die. What does toxoplasma do to the mind apart from schizophrenia?

According to Sydney University of Technology, men and women change differently when infected with Toxoplasma . Male carriers have shorter attention spans, slower reactions, a greater likelihood of breaking rules and taking risks, and are more independent, anti-social, suspicious, jealous and morose. These men are less attractive to women. Female carriers are more outgoing, friendly, more promiscuous, and are considered more attractive to men compared with the non-infected.

Studies have found that toxoplasmosis is associated with an increased car accident rate in people with Rh-negative blood. The chance of an accident is increased 2.5 times. Is the human being actually a puppet controlled by worms ?