Bacterial Rumen and Bacteria in Deep Sea Vents
Essential knowledge 4.B.2: Cooperative interactions within organisms promote efficiency in the use of energy and matter.
3. Interactions among cells of a population of unicellular organisms can be similar to those of multicellular organisms, and these interactions lead to increased efficiency and utilization of energy and matter.
To foster student understanding of this concept, instructors can choose an illustrative example such as:
• Bacterial community in the rumen of animals
• Bacterial community in and around deep-sea vents
Part One: Cow Stomach
The word ruminate is now associated with thinking thoughts over. It’s originally associated, however, with the way that cows and other animals, called ruminants, eat. Chewing is a multistep process with ruminants. They chew, swallow, regurgitate, and chew some more.
Grass is tough to digest—humans would starve if they tried to live off it—but cows and other ruminants have developed special stomachs that include an enormous region called the rumen.
The rumen is essentially a giant vat where prokaryotes (bacteria and archaea both) digest grass and other plants. Prokaryotes and ruminants work together to get food. Prokaryotes produce special enzymes calledcellulasesthat digest cellulose, the dominant compound in plant cells. Ruminants chew the food, and then chew it again to help give the prokaryotes better access to the nutrients in it.
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Analysis Questions: Answer Using Complete Sentences.
1) Why is the cow dependant upon the bacteria in its rumen?
2) Describe the digestive process of the cow. Does a cow really have four stomachs?
3) How do the interactions between the bacteria lead to increased efficiency and utilization of energy and matter?
Part Two: Bacteria in Deep Sea Hydrothermal Vents in Ocean
Within the hydrothermal vents of the deep sea, a myriad of bacteria and archaea live and prosper, despite being surrounded by heat, cold, pressure, and lack of light. These bacteria respond by using certain processes, described later, which enable them to survive.
Ever since scientists discovered deep-sea hydrothermal vents in 1979, studies have classified entire archaeal communities in deep-sea hydrothermal vent chimney structures. There may be aproximately ten to twenty thousand species ofbacteriaand archaea that roam the deep sea vents. Most of them rely on chemosynthesis, a process by which inorganic material is synthesized into new compounds with the ability to be used as energy for other organisms or itself.
The majority of the microbes that live in this niche include hyperthermophiles and thermophiles (heat loving bacteria) from both the bacterial and archaeal domains. Major types of bacteria that live near these vents are mesophilic sulfur bacteria. These bacteria are able to achieve high biomass densities due to their unique physiological adaptations. For example,Beggiatoaspp.is able to carry an internal store of nitrate as an electron acceptor that helps with the harvesting of free sulfide in the upper sediment region of the vents.
Recent studies have shown that large populations of extremely halophilic (salt loving) archaea inhabit the inside structures of black smoker chimneys. These bacteria belong to the genusHalomonasandMarinobacter. The existence of these halophilic archaea is probably due to the brines/salt deposits found in deep-sea hydrothermal systems.
The hydrothermal vent tubewormRiftia pachyptilais well known for its symbiotic relationship with sulfide oxidizing chemoautotrophic bacteria found in the cells of its trophosome tissue. The hemoglobin in the worms combines hydrogen sulfide and then gives this product to the bacteria. The bacteria, in return, give back carbon compounds to the worm. This interaction requires specific communications mechanism in both the bacteria and the worms. Scientists have found two classes of genes fromRiftiasymbionts that encode for environmental sensors, response regulators, and components of bacterial chemotaxis systems.
As far as the evidence shows, all the microbes involved within the deep sea vent ecosystem help the environment to survive and to thrive without the use of light, a key factor for other organisms in the ocean. Also, extremes such as heat, pressure and less nutrients play a role in how the microbes can adapt to the vents almost five to ten thousand feet below sea level. With so many types of bacteria within the ecosystem, it is likely that there is a lot of interaction between the microbes and other non-microbes, but as to what type of interaction is not quite clear. It is very difficult to examine these bacteria up close and bringing them (including the symbiotic organisms that depend on these bacteria) out of their habitat may perhaps permanently damage crucial bacterial pathways, and they usually do not survive the decompression when removed from the bottom of the ocean’s high pressure.
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Analysis Questions: Answer Using Complete Sentences.
1) What types of conditions must bacteria adapt to if they are to live in the deep-sea hydrothermal vents?
2) How do these bacteria live if they cannot photosynthesize?
3) Describe the interaction between tube worms Riftia pachyptilaand bacteria.
4) How do the interactions between the bacteria lead to increased efficiency and utilization of energy and matter?