Well everyone, the world has gone aghast with anything virus related, but I’m here to tell you that there are good viruses among us. In fact, life as you know it wouldn’t exist without viruses. So to help explain this, I’m going to take you on a little trip to Norway, so buckle up!
Hanging out in the ocean
There is a group of bacteria (roseobacters), that is extremely important to many aspects of global nutrient cycling, and exist in association with viruses. So one day, some of these guys were hanging out at a fjord in Norway, when this scientist caught some of them. Can you believe it?? They were just minding their own business! Anyway, these bacteria made their way back to a lab in a far-off land (well, Knoxville Tennessee, USA, to be exact). As luck would have it, some of their associated viruses made the long trip also. This study was very interesting because it helped us know who was there. Once we knew that, we could then figure out what they were doing.
Small but mighty
I’ve studied viruses for a few years (specifically those derived from a Norwegian fjord), particularly those that infect bacteria (a.k.a. bacteriophages, or phages for short). Picture this. As a matter of fact, I invite you to walk away from this text and just look at the strands of hair on your head for just a second.
Now that you’re back, just think: the bacteria from my research were 1/100th the diameter of just one strand of hair on your head. Then imagine…their corresponding phages were 1/1000th the diameter. Pretty tiny! But would you believe that despite their small size, phages are powerful enough to change cellular behaviour? Though these viruses are small, not all are. There is great diversity amongst viruses, and I don’t mean just by size.
I don’t think that we yet fully understand the breadth of diversity that exists among viruses. But luckily, there are some classification already formed. There are giant viruses, then really tiny ones (like mine!). Some have short tails (like those I’ve studied), long tails, or no tails whatsoever. Some infect humans, while others infect exactly one strain of bacteria. Yet others have different types of genetic material or different infection cycles. It is the diversity of infection cycles that helps identify some of the ‘good’ viruses and why they are interesting.
The good, the bad and the interesting
Viruses cannot make more of themselves on their own and therefore need a host to do this. But, in order for a mass viral exodus to occur (to get back into the environment), the host cell must be burst open. But not all viruses cycle in the same way.
Viruses are of different types. Viruses are really effective killers of their hosts, and some do it almost immediately (through a lytic cycle). Perhaps these could be thought of as ‘the bad’…from the host perspective of course. However, there are others that quite like their hosts, and can even integrate their genetic material, becoming one with the host so to speak (via lysogeny). These ‘good guys’ are said to offer protection from infection by other similar viruses (immunity), and can influence how a host cell grows, influence cell size, and dictate what genes are turned on or off, for example. The very interesting part of our study, and what formed the basis of our system, is that this protection was not seen. As a matter of fact, we initially infected a cell that already had a resident phage (originally, we had no idea!), with another, and the second virus even kicked out the first one!
The result was that we had the same host organism, but now one housed one virus, while another cell retained another very similar virus. This was just wild! What was crazier is that we observed differences in cell size and how the host cell attaches to surfaces (biofilm formation), among other changes.
Much more of this exciting research could be found in our scientific article, and there is increasing interest in the type of phages we used (temperate phages). We are still yet to determine how widespread this type of host-virus relationship is in the marine environment. Truly, the extent to how host and virus dynamically influence each other remains one of those secrets untold!
Reference: Basso, J.T.R., Ankrah, N.Y.D., Tuttle, M.J. et al. Genetically similar temperate phages form coalitions with their shared host that lead to niche-specific fitness effects. ISME J 14, 1688–1700 (2020). https://doi.org/10.1038/s41396-020-0637-z