Baby Bacteria

Sept. 26, 2014

By Medical Discovery News

Fetus in utero

While we know for sure that the bacteria living in and on us are key to our own well-being, more evidence suggests that we acquire our microbiomes before we’re even born. While a baby does acquire bacterial flora from its mother as it moves through the birth canal, scientists now think that our symbiotic, life-long relationships with bacteria begin in utero long before birth. They found bacteria living in the placenta, an organ previously thought to be sterile. They also discovered a baby’s bacteria to be similar to the bacterial flora of the mother’s mouth, making oral hygiene during pregnancy extra important.

An experiment in 2008 by Spanish scientists indicated that bacteria are acquired in some way before birth. They inoculated pregnant mice with labeled bacteria, which were then found in the meconium, the first bowel movement after birth. This was true even when the babies had been delivered by C-section. So scientists knew then that bacteria are acquired before birth and even without the birth canal, changing what we thought we knew about the womb.

Since then, scientists at Baylor College of Medicine have been studying the inside of the womb and birth canal in both humans and animals. They discovered that the vaginal microbiome changed during pregnancy, but it did not resemble that of newborns. So where did they get their bacteria from?

Baylor scientists then examined placentas from 320 women immediately after birth. Using DNA sequencing, they identified the individual types of bacteria each placenta contained. Comparing them to bacteria growing in and on the mothers, they found that the types of bacteria living in the mothers’ mouths most closely resembled those in their own placentas. Interestingly, the bacteria in the placenta consisted of high proportions of bacteria responsible for synthesizing vitamins and other nutrients, which probably benefits a developing fetus and newborn. So a fetus is first exposed to bacteria from the placenta, then at birth additional bacteria are introduced, and then again when babies are exposed bacteria on their parent’s skin, in breast milk, and in their environment.

Other studies have shown the influence of the microbiome on a mother and her baby. In one experiment, monkeys who ate a high-fat diet while pregnant and lactating produced babies with different proportions of bacteria in their guts than those of monkeys fed a normal diet. The short- and long-term consequences of abnormal maternal and infant microbiomes are not yet known, but it’s speculated that these changes could influence the metabolism of the infant and the development of metabolic disorders.

Science is increasingly aware of the role and importance the microbiome has in various parts of the body and the part it plays in human health and disease.

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The Human Genome Revisited

March 1, 2013

By Medical Discovery News

When scientists sequenced the human genome in 2000, it revolutionized biomedical research, much like the invention of the Internet forever changed communications. The project aimed to identify all the genes in the human genome.

At first, they estimated that humans had less than 100,000 genes, then improved methods lowered that to 35,000, and a new analysis suggests that humans have no more than 21,000 genes. When considering the complexity of a human being, that number does not seem very high.

However, even the highest of those estimates accounted for less than 20 percent of the DNA sequence in the human genome. The rest of sequence did not appear to encode genes that led to proteins and was therefore considered non-functional or “junk” DNA.

Now a recent study by more than 400 researchers at 32 institutions costing almost $300 million challenges that notion and suggests that more than 80 percent of the human genome is indeed utilized and therefore important in the overall biology of each person – so much for “junk” DNA. The Encyclopedia of DNA Elements (ENCODE) project concluded that 20,687 genes produce proteins and an additional 18,400 genes produce RNA involved in coordinating the activity of the genes that produce proteins. 

This extensive effort originally focused on the genomes of a small number of human cells but later expanded to include almost 150 different cells, including immune, embryonic, liver tissue, umbilical cord, and cancer cells. Specific genes produce proteins for different tissues at different stages of human growth, so using this wide array insured that the analysis included all active genomic regions and gave a broader view of the genome. 

The analysis also identified genome regions associated with specific human diseases, creating an opportunity for better understanding these diseases and treating them. In addition, the ENCODE project revealed just how different humans are from other mammals like monkeys, dogs, or dolphins. While previous estimates suggested that just 5 percent of the human genome is unique from other animals, ENCODE’s research doubled that estimate to almost 10 percent. Another revelation showed just how complex the control mechanisms of the human genome really are. They signal almost 20,000 genes at the exact time and location to allow a fetus to develop normally and instruct the specific workings of tissues, like in the kidneys, lungs, or brain.

So the action of genes is controlled by layer upon layer of interacting and intricate controls that make each person who they are. Homo sapiens are a species of biological wonder and will require many years of intense study to even begin to understand the mysteries of how genes are regulated to make a human being. 

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