Lesson 4 View the video “Microbial Evolution” and respond to

What Kind of Bacterium Cannot Tolerate oxygen?

About Microscopic Organism / September 16, 2019

Photosynthetic bacteria have been around for longer than the Earth’s atmosphere could sustain human life. It was only recently though that scientists began to unravel the mystery of how these micro-organisms execute the mechanisms of photosynthesis.

While scientists still have not been able to put all the pieces of the photosynthetic bacteria puzzle in the right places, they are actively studying them and are gaining valuable knowledge about the way they photosynthesize and how they have evolved. In fact, they believe that these micro-organisms may have had a huge impact on why the world evolved the way it did, and may show potential for life in places deemed uninhabitable, including extreme climates like Antarctica and even other planets.

What are photosynthetic bacteria?

Much like the name suggests, these micro-organisms are special types of bacteria that contain light absorbing pigments and reaction centers which make them capable of converting light energy into chemical energy.

Cyanobacteria contain chlorophyll while other forms of bacteria contain bacteriochlorophyll. Although bacteriochlorophyll resembles chlorophyll, it absorbs light of a longer wavelength than chlorophyll. Bacteriochlorophyll a is the most common form of bacteriochlorophyll but other forms include b, c, d, e, f and g.

Bacteria that contain bacteriochlorophyll do not use water as an electron donor and therefore do not produce oxygen. This is known as anoxygenic photosynthesis. Cyanobacteria perform photosynthesis using water as an electron donor in a similar manner to plants. This results in the production of oxygen and is known as oxygenic photosynthesis.

Classification of Photosynthetic Bacteria

Oxygenic photosynthetic bacteria perform photosynthesis in a similar manner to plants. They contain light-harvesting pigments, absorb carbon dioxide, and release oxygen. Cyanobacteria or Cyanophyta are the only form of oxygenic photosynthetic bacteria known to date. There are, however, several species of Cyanobacteria. They are often blue-green in color and are thought to have contributed to the biodiversity on Earth by helping to convert the Earth’s early oxygen-deficient atmosphere to an oxygen-rich environment. This transformation meant that most anaerobic organisms that thrived in the absence of oxygen eventually became extinct and new organisms that were dependent on oxygen began to emerge.

Cyanobacteria are mostly found in water but can survive on land, in rocks, and even in animal shells (or fur), and in coral. They are also known to be endosymbiont, which means they can live within the cells or body of another organism in a mutually beneficial way. Cyanobacteria also tend to live in extreme weather conditions, such as Antarctica, and are interesting to scientists because they may indicate a chance for life on other planets such as Mars.

Anoxygenic photosynthetic bacteria consume carbon dioxide but do not release oxygen. These include Green and Purple bacteria as well as Filamentous Anoxygenic Phototrophs (FAPs), Phototrophic Acidobacteria, and Phototrophic Heliobacteria. Let’s look at the differences between these types of bacteria a little more closely.

Source: photosynthesiseducation.com
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