Healthcare (Commonwealth Union) – A known fact is that when viruses infect bacteria—a frequent event in oceans, soils, and human guts—the interaction leads to the creation of entirely new organisms known as “virocells.” However, scientists are still unraveling how this microbial merger impacts and is influenced by their environment.
Four years ago, researchers made a surprising discovery in the lab involving ocean bacteria infected by two different viruses. The result was two distinct virocells, each functioning entirely according to the needs of their respective viruses as opposed to their bacterial origins.
Cristina Howard-Varona, a microbiology research scientist at The Ohio State University and the lead author of the study indicated that they are operating differently in spite the fact that they originated from the same parent cell. Essentially, the same entity transformed into two different entities because of two different viruses. She further indicated that it is fascinating because viral infections are constantly occurring.
This discovery was made under experimental conditions optimized to observe this previously unknown phenomenon, including high levels of the nutrient phosphate in the water. Howard-Varona and her team have since repeated the experiment in a new study, this time under low-phosphate conditions that more closely mimic the nutrient-starved pockets found in the natural ocean environment.
They discovered that real-world conditions significantly influenced how viral infections affected host bacteria. This impact was so pronounced that the study represented the two types of infected cells using a Venn diagram to illustrate their unique and shared functions and characteristics in low-nutrient atmospheric conditions.
The study was recently appeared in The ISME Journal.
The key takeaway from these findings is not just about the behavior of the two virocells in a low-phosphate area of the ocean, but also the profound effect the environment has on the common occurrence of viruses infecting bacteria.
“When you deplete only one nutrient, it has a drastic impact – it changes the picture of infection even though it’s the same cell and the same viruses as in the earlier study,” explained Howard-Varona. “So what would happen if we starved it even more or we deplete a different nutrient? This tells us it’s going to be very important to study cells and virocells under nutrient conditions that more closely resemble what they encounter in nature.”
Matthew Sullivan, a professor of microbiology at Ohio State and co-senior author of both studies, stated that the research holds promise for enhancing large-scale modeling of ocean microbial systems, which currently often overlooks the virocell component.
Sullivan, a professor of civil, environmental, and geodetic engineering and the founding director of Ohio State’s Center of Microbiome Science pointed out that if we want to predict how organisms affect ocean geochemistry, there is a need to understand the interactions within cell populations, how they acquire nutrients from their environment, and how this alters the composition of the organic matter that forms the cells. This comprehensive understanding is essential for assessing their impact on climate change and the oceans’ response to it,
Sullivan,further indicated that the same applies to modeling microbes in soils, which also lack nutrient-rich environments, the knowledge available about virocells and their contribution to root and crop health is still very limited.
In the recent study, researchers discovered that the two infecting viruses exerted significant control over the functions dominating the two resulting virocells. These viruses, known as phages, were chosen for their distinct characteristics. One phage, which is genomically similar to the host bacteria, focused on recycling existing resources. The other, less similar phage, had to exert more effort to generate resources. In both scenarios, the objective was to access energy, maximize viral replication, and ultimately destroy the host.
“But those differences were narrowed in the low-phosphate environment, so they’re less important – suggesting the environment may have a stronger effect than the infecting viruses on how virocells behave,” added Howard-Varona.
Additionally, both virocells exhibited common activities in response to starvation: initiating a cell-wide stress response, deriving energy from fat metabolism instead of carbohydrates, and decreasing their consumption of organic matter from the environment.
“Every cell in the world needs phosphate to make DNA and energy, and so without it, there’s no life, no function, no metabolism,” explained Howard-Varona. “And what we’ve shown is that in these conditions, virocells have commonalities. They sense the nutrient limitation and behave more similarly than they did when they were growing in a nutrient-rich environment.
