Category: Microbial Physiology
The double-edged sword called oxygen
By Ananya Sen
If you were to enter a time machine and go back to about 3.8 billion years ago, what would you find? Volcanoes spewing carbon dioxide, hydrogen, and methane into the atmosphere, some water, and no oxygen, which means that you would be dead in about six minutes. So how did humans, who are completely dependent on oxygen, come to exist? (more…)
Protein Translation Can Initiate From 17 Start Codons
In the realm of biology, we are always finding exceptions to the rule. And now, we have just added another exception to the central dogma of genetics.
But first, let’s review what the central dogma is. The central dogma states that that the flow of genetic information goes from DNA to mRNA to protein. In other words, DNA makes mRNA and mRNA makes protein. Of course, there are already exceptions to this flow as DNA can be made from RNA, for example. The sequence of nucleotides (the A’s, G’s, T’s, and C’s) in the DNA gets transcribed to mRNA (A’s becomes U’s, G’s become C’s, T’s become A’s, and C’s becomes G’s). During translation, groups of three adjacent nucleotides (called codons) in the mRNA signify what amino acids are used to build a protein. Since there are four nucleotides that make up DNA, there are in total 64 unique three-letter sequences that encode a total of 20 amino acids. (more…)
Giant Genes for Tiny Organisms
How big can a gene be? Ten years ago in the early days of genome sequencing, researchers scoured the genomes of 580 bacterial and archaeal species for large genes. They found that 0.2% of all genes identified are longer than 5,000 bases and 80 of them are “giant genes,” those larger than 15,000 bases. To put this in perspective, the average prokaryotic gene length is between 900 and 1,200 bases.
The two longest genes were found in the green sulfur bacterium Chlorobium chlorochromatii CaD3. The genes encode proteins 36,806 and 20,647 amino acids long and their corresponding genes would be 110,418 and 61,941 bases long, respectively. At the time of this research, these giant genes are only surpassed in length by the human titin coding sequence which is 38,138 amino acids long. Now, scientists have identified a slew of genes that exceed one million bases long. (more…)
Timeshares Are for Bacteria Too: Neighboring Biofilms Share Resources
Bacteria were once thought of as solitary individual organisms. We are finding out more and more that they behave quite contrary to this long-time perception. Bacteria form complex three-dimensional communities called biofilms. In biofilms, cells stick to each other and are encased in a sticky, slimy matrix proteins and sugars. It has been known for some time that cells within a biofilm communicate with one another. Now, researchers from the University of California San Diego and Universitat Pompeu Fabra determined for the first time, that neighboring biofilm communities communicate with one another to share resources. (more…)