Prof. Debbie Lindel's research group from the Faculty of Biology at the Technion embarked on three trips from Hawaii to the north and mapped the dramatic changes in the virus-bacteria relationship in the vast ocean. The group also discovered the "hot spot" - the undisputed area of control of the underwater viruses
The last two years have increased human awareness of the harms of viruses. And yet, not many know that there are viruses whose victims are... bacteria.
A study conducted by Technion researchers in the Pacific focused on cyanobacteria and the marine viruses that attack them - cyanophages. The research was led by Faculty of Biology researchers Prof. Debbie Lindel and postdoctoral student Dr. Michael Carlson.
According to Prof. Lindel, "Viruses are an important component of the Earth's biosphere and they shape the prevalence of microorganisms, their distribution, variation and development. That is why it is important to understand the effect of different environmental conditions both on the populations of the organisms and on the populations of the viruses that attack them."
Cyanobacteria are marine bacteria that perform photosynthesis - similar to plants. These bacteria know how to harness the sun's radiation to produce organic substances from carbon dioxide (CO2) ordered them unlimited underwater. The activity of these bacteria affects us in different aspects, and these are two of them: First, the byproduct of the photosynthesis process is oxygen, and these ancient bacteria provide the atmosphere with a significant portion of the oxygen that enables life on Earth. Second, cyanobacteria are an important part of the bottom of Food chain - They are eaten by larger creatures and thus, indirectly, feed the other marine animals, some of which also feed humans.
However, the cyanobacteria are not only threatened by predators but also by Cyanophages - marine viruses that infect them and cause their death. From the perspective of the cyanobacteria, cyanophages are evil and harmful enemies, but from a broad ecological perspective, these viruses play an important role in regulating the population of cyanobacteria.
And now - for the research conducted at the Technion. Said study, now published inNature Microbiology, based on Original molecular methods developed by the Technion researchers - methods that allow quantification of the cyanophages and estimation of the rate of infection of various marine bacteria by them. These are the tools with which the researchers mapped the distribution of these viruses and bacteria in the given area in the Pacific Ocean.
To collect the data, the research group conducted, in three consecutive years, three voyages from Hawaii to the north across three regions: Subpolar gyre , Subtropical gyre and the buffer zone between them - a total of 2,200 kilometers in the North Pacific. "As much as you expect," explains Prof. Lindel, "The water becomes colder, less salty and richer in nutrients - Nutrients - which affects both the cyanobacteria and the cyanophages. Our study aims to test the effect of these spatial changes on two types of cyanobacteria - Prolorococcus (hereafter PK), which is more common near Hawaii, and Synchococcus (hereafter SC), which is more common in the north - and the cyanophages that attack them."
The researchers discovered a strip 550 kilometers wide between the two regions (gyres), characterized by a particularly high prevalence of cyanophages per unit volume - sometimes up to 10 times that of the southern, subtropical region. so The cyanobacteria thrive precisely in nutrient-poor areas. In addition, the researchers discovered that in this strip, which they call a "hot spot", the infection of cyanobacteria by cyanophages increases. This strip creates a biological border between those areas.
To their surprise, the researchers discovered that In 2017 there was a dramatic change in the distribution of cyanobacteria and cyanophages In a hot spot in the Pacific Ocean. PC bacteria, which in previous years accounted for about 29% of the total bacteria in this area, dwindled to 5% in 2017 and their distribution is small. SC bacteria, on the other hand, thrived and their frequency and distribution increased relative to the previous years. "This surprised us and of course we wanted to understand the reason for the change - after all, the temperature remained reasonable for both species, we did not observe a lack of nutrients, and the concentration of lead, which may at a certain level be toxic for them, did not reach such a level. Our hypothesis was that the main cause of death that year was the viral infection - that is, cyanophage activity - which affected almost only the first type of bacteria."
The researchers found that In 2017, a significant increase of about 25% in the prevalence of cyanophages was recorded in the hot spot strip - an increase of half a million viruses per milliliter, compared to the previous years - and they infected much more cyanobacteria. "It was definitely a bad year for the PKK population. In our opinion, At that time, the viruses eliminated tens of percent of this population; However, since the second type, SC, grows and divides faster, it was less affected by the viruses and therefore managed to survive better, and the main damage was suffered by the PC population."
The study therefore shows that cyanophages may cause a dramatic change in the size of the cyanobacteria population and its geographical distribution - a change that has significant consequences for the marine ecosystem.
The research was conducted under the leadership of Prof. Lindel and Dr. Carlson with researchers from the University of Washington and the University of Hawaii. It is supported by a grant ERC (to Prof. Lindel) and a Fulbright Foundation scholarship (to Dr. Carlson) and the cruises took place within SCOPE and funded bySimons Foundation .
for the article in the journal Nature Microbiology click here
For pictures click here
- Prof. Debbie Lindel
- Dr. Michael Carlson
- Prof. Lindel in the laboratory in Anya
- The sample containers
- The sample containers rise from the water
- Scientific chart - the prevalence of cyanophages in the North Pacific Ocean as mapped by Technion researchers. The black line shows the sailing route in 2017-2016. The highest frequency is represented in yellow (the hotspot) followed in descending order by green, purple and blue.
Caption:
Credit: Technion barges
