Nav: Home

Rethinking role of viruses in coral reef ecosystems

May 22, 2017

Conventional wisdom has it that within virus-bacteria population dynamics, viruses frequently kill their host bacterial cells--a process called lysis--especially when there's a large concentration of bacteria. A different dynamic called lysogeny, in which viruses lie dormant within their host cells but don't kill them, has been thought to be a relatively rare phenomenon, mostly occurring at low bacterial concentrations.

But a new study led by researchers at San Diego State University's Viral Information Institute suggests conventional wisdom has it wrong: Lysogeny might be far more common than previously thought and may even become more prevalent when hosts are densely packed in an ecosystem, which often occurs when environments are stressed. These findings could lead to a better understanding of degraded coral reef ecosystems and how to preserve them.

Algal blooms, fungal blights and bacterial infections are just a few of the ways that microbes can rapidly increase in density within an ecosystem. How viruses respond to such events is of great interest to ecologists. Traditionally, most researchers have assumed that when microbe populations boom, the viruses that inhabit them start replicating inside them--the lytic phase--boosting their own numbers but killing off their hosts.

"This suggested that lysogeny provides a temporary refuge for viruses when hosts are starving and scarce," the authors of the recent paper wrote in the study.

Previous research by Ben Knowles, a postdoctoral scholar at Rutgers University and a former graduate student within SDSU virologist Forest Rohwer's lab, upended the conventional theories of viral dynamics with the discovery of viruses that stayed lysogenic even as their host cells became more and more densely concentrated within their ecosystem. SDSU's Viral Information Institute, one of the university's self-identified areas of excellence, is among the world's leaders in researching viruses that replicate inside bacteria, otherwise known as bacteriophages.

"These earlier findings fundamentally flipped the dynamics of virus-host interaction," Knowles said.

Hoping to learn more about how viruses behave as their host numbers wax and wane, Knowles and colleagues performed a meta-analysis of 39 publications that tracked this pattern and found something surprising: There was no correlation at all between the density of host cells and whether their viruses were lytic or lysogenic, the researchers reported in the journal Nature Microbiology.

Knowles said these results should encourage microbiologists to re-calibrate population models that include virus-bacteria interactions, such as those commonly used to predict how sensitive ecosystems like coral reefs might respond to microbial overgrowth such as algal blooms and bacterial invasion.

Unfortunately, incorporating lysogeny into these models is difficult. If viruses aren't killing off hosts in predictable ways, the dynamics quickly become chaotic and hard to measure, Knowles explained. Further research might reveal precisely why viruses switch over from dormant freeloaders to replicating killers, but doing so will likely require genomic analyses of single cells--a process that is currently prohibitively expensive for large-scale projects.

Until then, the study's findings underscore how little we know about viruses and how they fit into their ecological niches, Knowles said.

"We've long thought about viruses as killers because that's what fit the models," he said. "But the way viruses interact with their hosts is much more complicated than that."
-end-


San Diego State University

Related Bacteria Articles:

Conducting shell for bacteria
Under anaerobic conditions, certain bacteria can produce electricity. This behavior can be exploited in microbial fuel cells, with a special focus on wastewater treatment schemes.
Controlling bacteria's necessary evil
Until now, scientists have only had a murky understanding of how these relationships arise.
Bacteria take a deadly risk to survive
Bacteria need mutations -- changes in their DNA code -- to survive under difficult circumstances.
How bacteria hunt other bacteria
A bacterial species that hunts other bacteria has attracted interest as a potential antibiotic, but exactly how this predator tracks down its prey has not been clear.
Chlamydia: How bacteria take over control
To survive in human cells, chlamydiae have a lot of tricks in store.
More Bacteria News and Bacteria Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Anthropomorphic
Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#534 Bacteria are Coming for Your OJ
What makes breakfast, breakfast? Well, according to every movie and TV show we've ever seen, a big glass of orange juice is basically required. But our morning grapefruit might be in danger. Why? Citrus greening, a bacteria carried by a bug, has infected 90% of the citrus groves in Florida. It's coming for your OJ. We'll talk with University of Maryland plant virologist Anne Simon about ways to stop the citrus killer, and with science writer and journalist Maryn McKenna about why throwing antibiotics at the problem is probably not the solution. Related links: A Review of the Citrus Greening...