The ocean has an endless supply of life forms and topics to write and learn about. Nonetheless, sometimes I sit in my living room staring into space and wonder what the topic of the next amazing nature column should be.
On the last such occasion, my son asked if I had ever written about bacteria. I have not, and at first I wondered how to write about those minute life forms that in most people only spur images of disease.
There are many different bacteria. Few of them cause disease. Many are harnessed in the making of medicines, alcohol and various foods — cheese, for example. Without the help of our natural suite of internal bacteria, we suffer indigestion. Bacteria are everywhere we look, so it is not surprising that they can also be found in the ocean.
Life itself originated in the ocean and for several millions of years bacteria were the only life forms on this planet. While bacteria are small and lack some of the complex structures of the cells of plants and animals (the main difference is the lack of a cell nucleus), their tolerance to harsh living environments outshines that of more complicated life forms.
Some bacteria can use the energy set free in chemical reactions. As early as 3.4 billion years ago, bacteria used sunlight for their energy needs, leaving sulfur or sulfate as waste products. Today, in the deepest and darkest reaches of the ocean, where the earth itself vents toxic hydrogen-sulfides, bacteria not only eke a living from breaking up chemical compounds but form the base of a vast ecosystem of numerous organisms independent of sunlight.
We owe our life to a group of bacteria called Cyanobacteria that started 2.7 billion years ago to use the sunlight energy to break carbon dioxide into carbon and oxygen. They used carbon to thrive and grow; they discarded the oxygen into the atmosphere. This was not nice to their fellow life forms because oxygen was (and is) toxic to many bacteria. Thus, Cyanobacteria caused a major environmental havoc on early earth, driving most of the bacterial life forms of their time into hiding and set the stage for organisms that could tolerate the poisonous oxygen.
The process of photosynthesis became popular among the later developing seaweeds and plants. Not to be left out of the picture, animals devised a complicated mechanism that would use that oxygen, bind it to hydrogen and carbon in a process called respiration and gain energy and the use of other nutrients.
What is the most common organism on earth? There is a bacterium called “Pelagibacter ubique”. The total number of this bacterium and its relatives on earth is estimated at a number that I have no name for: it is a 2 followed by 29 zeros. It is probably the most abundant bacterium on the planet and makes up about 25 percent of all bacterial cells in the open ocean.
“Pelagus” means sea, “bacter” means rod or bacterium and “ubique” is Latin and means “everywhere.” Translated, we have the “bacterium of the sea everywhere.”
However, in February this year an article was published in the journal nature claiming that not Pelagibacter ubique was the most common life form, but rather a little pest that attacks it. This organism is a bacteriophage (kin to a virus) and was described “probably the commonest organism on the planet.”
Considering that we are discussing something so small we can’t even see it, which is plagued by something even smaller in numbers so large we can’t name them, there are a lot of superlatives in this topic!
It should not surprise you then if I mention that bacteria are of uttermost importance also in the planet’s carbon cycle, namely the recycling of organic matter into nutrients for new growth and the continuation of the cycle of life. In the ocean around us, all those billions of pelagibacter have been busy over the winter providing nutrients.
This spring, the phytoplankton can scoop up the nutrients and grow in the returning sunlight, feeding all the small animals, which feed the young fish, which are eaten by the bigger fish, some of which will again be eaten by us this summer, if we are lucky. Without bacteria, there wouldn’t be fish in the ocean or food on your table.
Switgard Duesterloh, Ph.D., is an assistant professor of natural sciences at Kodiak College. She operates the Kodiak Ocean Science Discovery Lab and teaches ocean science to students throughout the Kodiak Island Borough School District.