Researchers from the universities of La Laguna and Vienna, in addition to other scientific centers, have found that bacteria from the mesopelagic layer, between 200 and 1,000 meters deep in the oceans, can fix CO2 with inorganic sulfur as the only source of energy.
Federico Baltar, from the Austrian institution, and José Manuel González, from the Microbiology area of the Tenerife center, direct the study that has been published by Nature Microbiology, as reported this Friday by the University of La Laguna on its institutional page. Despite being invisible, microorganisms are of great importance in the global carbon cycle due to their abundance and activity, explains the teaching center.
As an example, he indicates that unicellular algae and cyanobacteria in the oceans are responsible for approximately half of the global CO2 fixation, a process that is only part of the global carbon cycle, since practically all this organic matter is remineralized. again due to the activity of a wide diversity of bacteria found in the water column.
But there is less information about the relevance of the CO2 fixation process in deep areas where sunlight does not reach, and the difficulties in carrying out research are obvious, since they are less accessible areas and, therefore, less studied than the surface where sunlight penetrates (photic zone).
This photic zone is barely a thin layer compared to the dark ocean, which represents a much more extensive environment: the average depth of the ocean is 4 kilometers, while light does not penetrate from 50 to 200 meters. .
Given the importance of the dynamic balance of carbon in the atmosphere, the scientific community is interested in knowing those biological processes that regulate its transformation.
Microorganisms in the oceans, which are estimated to account for about two thirds of the biomass in the marine environment, play a central role in the biosphere.
The researchers carried out a sampling point on the Ross Sea ice shelf, in a hole that measures approximately 30 centimeters in diameter and 400 meters deep until reaching liquid water. In this frigid environment, a certain group of bacteria that dominates the community of sulfur oxidizers was found for the first time.
There have only been two expeditions in which liquid water under the ice has been reached, the first in 1977 and the second in 2017, despite multiple attempts. This study is a continuation of a previous one by the same group of researchers on bacterioplankton under the Ross Sea layer in Antarctica.
This article, which was published at the time in the journal Nature Communications, suggests the existence of bacteria that use sulfur or nitrogen species as an energy source and also finds that the diversity of bacteria is similar to that of other areas of the oceans.
In the same line of research, the team has published this new article in which more details are provided about the microorganisms under the Antarctic ice sheet and the deep ocean. It describes a group of bacteria abundant in polar areas, as it had been found in principle, but also in the rest of the oceanic regions of the planet, although only in the dark ocean.
They live in environments ranging from frigid waters, with temperatures below 0ºC at the poles, to more temperate areas near the equator. These bacteria have the ability to use different inorganic sulfur compounds and the researchers specify that elemental sulfur, hydrogen sulfide and other derivatives of inorganic sulfur serve as an energy source to survive in this extensive environment and, at the same time, so scarce in energy sources.
In the article, the researchers apply molecular and bioinformatics techniques to study the microorganisms that inhabit this part of the planet. As a result, the study provides new experimental data on the CO2 fixation capacity of these microorganisms, which point to this group of bacteria as dominant in the inorganic sulfur oxidation process in the mesopelagic.
The research provides information on the processes of the cycles of the elements, sulfur and carbon, in which the activity of microorganisms has special relevance as the ultimate regulator of the composition of the atmosphere.