New Research Reveals Insight into Life’s Minimum Complexity
After being married for nearly 24 years and raising three daughters, I have come to appreciate that women are much more complicated than I could have ever otherwise imagined. And I don’t think that I am alone in that revelation.
Studying biochemistry for the last three decades, has led me to appreciate the complexity of biochemical systems. They are far more detailed and intricate than I could have ever imagined when I began my studies as a graduate student. And, once again, I am not alone in that insight. As noted a few weeks ago, based on recent advances, many life scientists now recognize that the biochemical complexity of even the simplest life-forms is much more extensive than anyone could have initially envisioned.
Scientists have estimated that an organism’s genome must contain at minimum about 400 genes (this is called the essential gene set) to even be recognized as living. My books Origins of Life and The Cell’s Design both discuss this in detail. (Go here for a brief description of recent work on life’s minimal complexity.)
Recently a team of researchers went one step further in this work by examining the interactions that take place between the gene products of a minimal organism, Mycoplasma pneumoniae. This microbe, one of the simplest known bacteria, is an obligatory parasite that has a reduced genome relying on the biochemistry of the host for many essential biochemical functions.
The researchers characterized the interactions of this microbe’s gene products at three levels. The first involved the RNA molecules produced by the genome. RNA molecules play a role in mediating the biochemical expression of the information harbored within genes. The cell’s machinery uses the information in genes to make proteins. But to do so, first requires the production of RNA molecules which transmit information from the genes to ribosomes where the proteins are made. Cell machinery can control the amounts and types of proteins it produces by regulating the amount and types of RNA transcribed from genes. The scientists monitored M. pneumoniae’s production of full sets of RNA molecules under various growth conditions. They were surprised to learn that despite the microbe’s seeming simplicity its pattern for producing RNA molecules is much more intricate and involved than expected, resembling that of complex organisms like plants, fungi, and animals.
Additionally, the researchers studied the way the microbe used protein molecules once they were produced at ribosomes. It turns out that individual protein molecules participate in multiple roles in the cell’s operation with some of them taking part in more than one different type of protein complex. The team also examined the metabolic processes of M. pneumonia. They discovered that in many instances the enzymes that carry out the cell’s metabolic activities participate in more than one metabolic route.
Though this microorganism has a small genome, it is remarkably flexible in its ability to respond to changes in the environment. This flexibility is possible because of the sophisticated gene expression patterns and the multifarious functions its proteins and enzymes play. The unexpected number of interactions among the biochemical components and systems arises because protein complexes and metabolic pathways share proteins and enzymes, making M. pneumoniae much more complex than its genome size suggests.
Most biologists regard the genome size of an organism as a good indication of its complexity. But this new work reveals that such a standard can grossly underestimate complexity. The network of biochemical interaction arising from the shared components of protein complexes and metabolic pathways are more complex than the list of genes in a genome would immediately suggest.
The surprising intricacy of even the simplest bacteria creates problems for the evolutionary paradigm. Even in its minimal form, life is unimaginably complex. And this complexity has to be accounted for in all origin-of-life models. In other words, the models must account for the simultaneous occurrence of a relatively large number of gene products, as well as the multifaceted network of interactions the gene products engage in to make life operate at even the most rudimentary of levels. And as I discussed last week, the proteins that take part in these reticulated interactions are also spatially and temporally localized within the cell throughout the course of the cell cycle, further exacerbating the problem for evolutionary explanations of life’s emergence.
Complexity, in and of itself, is not evidence for the work of an intelligent Agent, but these latest studies indicate that the immense biochemical complexity of even the simplest microbe reflects order and organization, which are markers for design.
Based on these latest results, I think it’s safe to say biochemical complexity far out paces that of women—I just happen to have a better grasp on the previous.
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