This is according to a joint study by researchers from the Technion and the Massachusetts Institute of Technology who studied the connections between viruses and their hosts
Scientists in the Department of Civil and Environmental Engineering at MIT and the Technion documented for the first time the entire genomic expression of a virus-parasite and the host bacterium during eight hours of viral infection. The results of the study are expected to bring scientists from different fields to re-examine their approach to studying the relationships between viruses and their hosts - interactions that apparently play a central role in the transfer of genes between different species.
Dr. Debbie Lindel of the Faculty of Biology at the Technion and Professor Sally Chisholm of MIT and their colleagues report in the latest issue of the journal Nature that following their research on a system containing the marine bacterium Prochlorococcus, they hypothesize that viral infection may play a significant role in determining The genetic repertoire of families of bacteria - even when the specific infected bacteria dies.
This may indicate that the meeting between the marine host and the virus may not only be a "battle" between two individuals, but also a significant mutual evolutionary process, which helps both species to improve their adaptation to life in the ocean.
"The current status of the host-virus relationship has been influenced by a rich history of interactions," explains Dr. Lindel. "Although we cannot accurately map all events in the same evolutionary history, our findings suggest a new mechanism that results in the mutual exchange of essential genes between host and virus."
Since the genomic expression pattern in this host-virus system is significantly different from systems known from previous studies - such as that of the bacterium E coli and the virus known as T7 - the current study is expected to lead to the recognition of the need to study different types of marine bacteria and not be content with relying on a single system as a model.
"We hope that this work will encourage scientists to investigate a wide range of host-pathogen systems, and that this change will lead to a significant expansion of our understanding regarding the variety of interactions that exist in nature between a host and a pathogen," said Professor Chisholm, one of the discoverers of Prochlorococcus in 1985. "More than Thus, these studies will help us understand the role that those interactions have in shaping the microbial ecosystems."
Only in the last few decades have researchers begun to discover and study important marine bacteria such as Prochlorococcus, which play a very important role in our lives. These photosynthetic bacteria are single-celled bacteria that use light energy to produce oxygen and organic carbon - and provide a significant portion of the oxygen we breathe - and form the basis of the food chain that exists in the ocean.
In host-virus systems that have already been studied, the bacterium "hijacks" the host cell and immediately "locks" its genomic expression. This prevents the bacteria from carrying out its metabolic processes. The attacking virus directs the expression to its own genome, and activates the genes it needs. In other words, it replicates itself rapidly at the expense of the host.
In contrast, in the system of Prochlorococcus and the P-SSP7 virus, increased expression occurred in 41 of the bacterium's 1,717 genes. That is, the researchers discovered increased amounts of the RNA - the "messenger" from these genes in the cell, during the infection process. The increased expression of so many genes of the host during infection is a phenomenon that has not yet been observed in the world of bacteria.
Furthermore, many of the host's genes amplified during infection are among those found in the host's "genomic islands". These are regions that are "hot" sites for genomic exchanges between host and virus. In this case, some of the genes transferred back and forth are related to proteins that affect the bacterium's ability to adapt to environmental changes such as lack of nutrients and light deprivation. The scientists hypothesize that the bacteria's genes underwent changes when they were inside the virus, and these changes led to the creation of new versions of a protein, which give the bacteria an improved ability to withstand environmental changes. It is also possible that many copies of the same gene may confer an advantage.
In addition to this, the viral genome contains genes that were transferred from hosts in bacteria, and within these genes energy-producing proteins are encoded, including photosynthesis genes that the bacterium Prochlorococcus needs for metabolism and DNA replication. Although these genes are located far from each other in the viral genome, they are copied during the infection at the same time and not in the usual order - from left to right. This fact leads researchers to hypothesize that the virus is trying to keep the host alive so that it continues to provide it with the energy it (the virus) needs for DNA replication.
Lindel and Chisholm believe that the main explanation for the increased genetic expression and gene exchange is that the bacterium activates certain genes in response to infection, as a means of self-defense. The virus "learned" to use these genes to its advantage, and integrate them into its own genome. Then, when the virus attacks another bacterium, it increases the same genes itself to improve its "settlement" in the host bacterium. When a bacterium survives infection, the same improved genes integrate back into the bacterium's DNA in "genomic islands", improving the chances of the bacterium and its offspring surviving in the harsh marine environment.
"These viral parasites cooperate with the hosts during the infection, and provide proteins that probably function in the metabolic system of the host and thus it squeezes every drop of energy from them before eliminating them," says Dr. Lindel. "But in evolutionary terms, such host-pathogen interactions affect the evolution of the genome content of both the host and the virus, thus affecting their ability to colonize new environments."
Later in the study, the question of whether the bacterial genes that develop in the virus do indeed give the virus a survival advantage, and after being transferred back to the bacterium - to it as well.
