Why microbes in the deep ocean live without sunlight

Date:
February 6, 2023
Source:
Monash University
Summary:
A new study reverses the idea that the bulk of life in the ocean
is fueled by photosynthesis via sunshine, revealing that many
ocean microbes in fact get their energy from hydrogen and carbon
monoxide. It has always been a mystery as to how microbes growing
in deepest parts of the sea survive, with no sunlight. A new study
shows that a distinct process called chemosynthesis -- growth
using inorganic compounds -- fuels microbes in these darkest depths.


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FULL STORY ==========================================================================
A world first study reverses the idea that the bulk of life in the ocean
is fuelled by photosynthesis via sunshine, revealing that many ocean
microbes in fact get their energy from hydrogen and carbon monoxide.


==========================================================================
It has always been a mystery as to how microbes growing in deepest parts
of the sea survive, with no sunlight. A new study, from researchers at
the Monash University published in the journal Nature Microbiology,
shows that a distinct process called chemosynthesis -- growth using
inorganic compounds -- fuels microbes in these darkest depths.

The five-year study, led by Dr Rachael Lappan and Professor Chris Greening
from the Biomedicine Discovery Institute, reveals that two common gases
-- hydrogen and carbon monoxide -- serve as the fuel for trillions of
microbes in the ocean from the tropics to the poles.

According to Professor Greening, until now most scientists have believed
that ocean microbial life is primarily driven by photosynthesis (growth
by using light energy). "But what about those regions so deep that light
can't penetrate or so nutrient-poor that algae can't thrive? We showed
in this study that instead chemosynthesis is dominant in these regions,"
he said.

"Hydrogen and carbon monoxide in fact "fed" microbes in all regions
we've looked at: from urban bays to around tropical islands to hundreds
of metres below the surface. Some can even be found beneath Antarctica's
ice shelves." The study involved combining chemical measurements during oceanic voyages with laboratory-based characterisation of microbial
cultures. The research team also extensively used metagenomic sequencing, "which tells us the genetic blueprints of all of the microbes present
in a given region of the ocean," Dr Lappan said.

"We found the genes that enable hydrogen consumption across eight
distantly related types of microbes, known as phyla, and this
survival strategy becomes more common the deeper they live." For this
project, the researchers were inspired by their previous work on soil
bacteria. Professor Greening and colleagues have previously showed most
soil bacteria can live by consuming hydrogen and carbon monoxide from
the atmosphere.

"The surface layers of the world's oceans generally contain high levels
of dissolved hydrogen and carbon monoxide gases due to various geological
and biological processes. So it made sense that oceanic bacteria used
the same gases as their terrestrial cousins," Dr Lappan said.

These findings provide insights into how life evolved. Professor Greening concludes that "The first life probably emerged in deep-sea vents using hydrogen, not sunlight, as the energy source. It's incredible that,
3.7 billion years later, so many microbes in the oceans are still using
this high-energy gas and we've completely overlooked this until now."
* RELATED_TOPICS
o Plants_&_Animals
# Soil_Types # Microbes_and_More # Organic #
Marine_Biology
o Earth_&_Climate
# Air_Quality # Global_Warming # Oceanography #
Energy_and_the_Environment
* RELATED_TERMS
o Microorganism o Photosynthesis o Phytoplankton o Carbon_cycle
o Plant o Sea_water o Chloroplast o Ocean

========================================================================== Story Source: Materials provided by Monash_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Rachael Lappan, Guy Shelley, Zahra F. Islam, Pok Man Leung, Scott
Lockwood, Philipp A. Nauer, Thanavit Jirapanjawat, Gaofeng
Ni, Ya-Jou Chen, Adam J. Kessler, Timothy J. Williams, Ricardo
Cavicchioli, Federico Baltar, Perran L. M. Cook, Sergio E. Morales,
Chris Greening. Molecular hydrogen in seawater supports growth
of diverse marine bacteria. Nature Microbiology, 2023; DOI:
10.1038/s41564-023-01322-0 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/02/230206130626.htm

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