THIS WEEK IN ENVIRONMENTAL HEALTH

WEEK 2: SEPTEMBER 8 - 11, 1998

OBJECTIVES - LECTURE #2

At the conclusion of today's session, you should know:

1. The importance of bacteria in the formation of the Earth and the evolution of Earth's inhabitants.

2. Some of the major events in modern microbiology and their impact on our lives today.

3. Several ways that microbes benefit the natural environment and human life.

4. Several types of microbial interactions with other living things.

Vocabulary -- Week 2

inorganic compound --- compound that does not contain carbon.

organic compound --- compound that contains carbon and hydrogen (other elements may also be present).

element --- chemical composed of only one kind of atom.

molecule --- smallest quantity of a compound that retains the properties of a compound.

compound --- a substance composed of two or more chemical elements.

amine group --- chemical compound containing nitrogen and hydrogen.

protein --- macromolecule composed of a specific sequences of amino acids.

primordial --- rudimentary or earliest.

stromatolite --- a rocklike structure formed by layers of fossilized algae

mutant --- a change in the characteristics of an organism due to an alteration of the genetic material.

hydrovent --- holes in the ocean floor through which steam and molten rock flow.

archeabacteria --- a group of bacteria believed to be of ancient origin that frequently exist in hostile environments

oxidation --- the union of oxygen with another chemical element

metabolism --- the sum of all biochemical processes taking place in a living cell.

The Golden Age of Microbiology --- period of time between 1857 - 1914, when scientists rapidly developed means of studying and growing microorganisms.

species --- the fundamental rank in a classification series.

symbiosis --- close association of two dissimilar organisms living together.

neutralism --- an association between two organisms in which one species is dormant, and the other merely supports the other.

spore --- reproductive structure formed by some fungi, bacteria and a few primitive plants.

commensalism --- one species benefits and the other is not affected by the relationship.

anaerobic bacteria --- bacteria that grow in the absence of oxygen.

aerobic bacteria --- bacteria which require oxygen for growth.

mutualism --- symbiotic relationship in which both members of the relationship benefit.

lichens --- symbiotic relationship between a fungus and an alga or a cyanobacteria.

biofilm --- surface aggregate of composed of layers of bacteria embedded in a bed of slime.

normal flora --- microorganisms that live on body surfaces in a harmonious relationship with their host.

host --- the organism on or in which another organism lives.

antagonism --- symbiotic relationship in which one organism harms the other.

pathogen --- disease causing microbe

parasite --- organism that lives in or on a host organism from which it secures advantage.

Study Questions - Week 2

1. Which of the following combinations of gases surrounded the Earth 5 billion years ago?

a. oxygen and carbon dioxide

b. nitrogen and oxygen

c. carbon dioxide and nitrogen

d. nitrogen and hydrogen

2. What organisms were the first to live on Earth? Where did they live?

3. What did these bacteria produce that made it possible for the eventual evolution of mammals?

4. What are stromatolites and how do they form?

5. Differentiate between organic and inorganic compounds.

6. Name three major events during the "Golden Age of Microbiology".

7. List five things that you have used or eaten today that were influenced in their production by microbes.

8. Explain the claim made in class: "Bacteria are responsible for the Brooklyn Bridge."

Lecture #2 --- ENV 103

OLDER THAN DIRT: THE ROLE OF MICROBES
IN THE GREATER SCHEME OF THINGS

1. Bacteria and the History of the Earth: Don’t Start a Home without them!

(Overhead with colored timeline.... add "markers" as you go along in story....)

Has any of you ever visited Meteor Crater in Arizona? I did several years ago --- followed by the Grand Canyon. Meteor Crater to me was just as awesome -- if not more so-- than the Canyon. Why? Because of how quickly it was formed... and the power by which it was formed. Almost a mile across, it was formed 50,000 years ago --- in about 10 seconds. A meteor, made of iron and lead, slammed into the Earth and left this gigantic pock mark.

Within seconds... fractions of seconds.... rocks were crushed and melted; all living forms vaporized. Steam and dust and debris filled the atmosphere for hundreds of years.

For millions of years preceding this event, smaller particles of material had been bombarding the earth, bringing microscopic particles of inorganic matter, such as metals, and organic compounds.... substances which contain carbon and hydrogen, elements necessary for life.

Some of these microscopic dust particles still reach Earth today, bringing the same elements that they have for over 5 billion years.

a) 5-6 billion years ago... the firmament was formed from cosmic dust particles from comet, meteors and asteroids that were constantly "dirtying up" the space that we now know as our solar system. The particles began to coalesce into a swirling firmament, surrounded by carbon dioxide and nitrogen.

b) 4.2 bya...The gases combined with organic molecules from the minute particles coming through the gaseous layers, and hydrogen and oxygen combined to form water.... lots of water.... and it continued to do so until the entire surface was covered with water.

c) 4.0 bya.... The waters... which we will now call oceans.... tumbled and grumbled and continued to collect a wide diversity of molecules from the still bombarding particles. Some of these compounds reacted with the water molecules to give dissolved or hydrated forms of some molecules, while others reacted with one another to form yet new molecules, more complex and diversified than the earlier ones. These compounds were amine groups then RNA The RNA molecules were capable of replicating themselves, and mutating, thus forming proteins. This big cover of nourishing liquid resembled a good old fashioned soup, into which everything good and tasty had been thrown... a nice, warm primordial soup! We don’t know exactly how RNA came into being. (DNA was still a twinkle in the eye of the Creator.)

d) 3.5 bya... The primitive RNA was subjected to the light from the infant sun, which illuminated with only about 70% of its current energy. Other molecules introduced from the surrounding liquid or from the constant rain from outer space enveloped the RNA and other molecules... which, in turn became factories... of life! The rose to the surface of the waters seeking an unknown energy, Some of the inclusions of these enclosed proteins were chlorophyll, which, when exposed to sunlight and the CO2 of the earth’s atmosphere, produced energy by which they could live and multiply. As a byproduct of this reaction, they expelled a new gas into the atmosphere above the waters... oxygen.

As these oxygen producers grew and multiplied, they became what we now call cyanobacteria. The bacteria soon formed velvety mats in some areas of the waters. These mats trapped particles within their close confines, adhering these substances with a sticky sheath on their cell walls. As the mats became heavy with inorganic compounds, the sun-seeking cyanobacteria kept climbing to the surface, leaving layers of calcium carbonate and dead bacteria in their wake. These primitive stratified rocks, called stromatolites, are very important in the study of the age of the Earth. This ancient association is still in existence today in Shark Bay, Australia, much as they were 3.5 billion years ago.

The bacterial mats became thicker and thicker, allowing less and less sun to reach them. The ritual of the survival of the fittest promoted mutants which were learning to exist without the sun and without oxygen. Some sank to the lowest levels of the ocean’s floor; some even became acclimated to the high temperatures around the hydrovents opening through the ocean’s floor, spewing out the heat and steam from the molten interior earth.The organisms are now known as the archeabacteria.

e) 2 bya.... The bacteria have now produced enough oxygen to react with many elements within the ocean’s waters to form oxidized compounds, such as iron oxide. The O2 levels in the atmosphere have reached about 21% of the total gases... the level which we have today. The single celled cyanobacteria mutated many times over as the bacteria themselves began to use oxygen in their metabolisms. They developed complex internal structures called organelles which allowed them to metabolized more efficiently... and perform more complex tasks.

f) 1 bya.... The "new" bacteria, which had now progressed from the simple RNA proteins to the larger DNA molecules and complex carbohydrates, had an organized compartment for the DNA, a nucleus... the eukaryotes had come to Earth. These organisms also learned that they could survive better if they exchanged their DNA material. Some of the organisms developed from one cell to multicelled organisms, some with specialized cells for transfer of their DNA. Thus, sex was born in the warm waters of the oceans... and originated with our little friendly bacteria.

(Question --- Did you know that bacteria built the Brooklyn Bridge? Walk through the sequences....)

2. "Modern" Microbiology

It has been only within the past 150 years that the study of microorganisms has flourished. The years 1857-1914 are referred to as "The Golden Age of Microbiology". It was during this time that many rapid advances were made, with Louis Pasteur and Robert Koch as its leaders. During this period, microbiologists studied the chemical activities or microorganisms; perfected means of culturing them, and improved microscopy methods. Many vaccines and sterile surgical techniques came from this period.

(Overhead & handout: Golden Age)

So... we see that the bacteria are really responsible for where we are today... and how we live today.

(Overhead..."A Sampling of Benefits Derived From Microorganism and Their Activities". Discuss things listed.)

3. Microbial Interactions

microbes do not like the single life... in fact, they operate better in the company of others. It is rare to find a single type or species or microbe alone in nature; in fact, in order to survive, they must be in close association with other microbes or plants or animals. These relationships are called symbiosis, and can be beneficial, harmful or neutral for the organisms involved. To become a permanent member of any community, a microbial species interacts with and influences other organisms. To survive, it must compete for nutrients and overcome any competition. Sometimes its presence changes the environment for other organisms.

Neutral interactions are likely only when one organism is in a dormant state or when one organism is solely a support on which the second one grows. An example of this would be a mold spore, which is a dormant phase of mold, found on another organism.

Commensalism --- One species benefits and the other is not affected by the relationship. An example of this in the microbial world can be found in the human intestine, where billions of microorganisms are necessary for the complete digestion of food. Some of the beneficial bacteria here are anaerobes, bacteria which are killed in the presence of oxygen. Other bacteria present can tolerate both aerobic (with oxygen) and anaerobic environments and utilize the oxygen, thus protecting the anaerobic bacteria.

Mutualism --- Both partners in the relationship benefit here. An excellent example of this type of relationship is lichens. (Remember last week, one of our grab bag items was a lichen... you were stumped by it, and I said it was a combination of algae and a fungus.) Lichens are usually found in habitats that don’t have much in the way of nutrients or water. Thus, the algae, being photosynthetic, provides the fungus with oxygen and nutrients, while the fungus, may use its filaments to act like roots and protect its partner from dehydration and supply it with essential minerals. In this way, the two organisms can live in less than ideal environments. Lichens can be found on granite boulders, in deserts, and in Arctic areas.

Biofilms are another example of microbial mutualism. Many species join together and form complex aggregate communities, forming thin sheets of slime on the surface of objects. This can be ponds or the surface of your teeth. Or, they can be found in sewage ditches or contaminating surgical instruments.

Microbial mutualism can also occur between microbes and plants... nodules on clover roots for nitrogen fixation; fungi with plant roots, to increase ability to absorb from the soil.

With animals, microbes provide protection in the form of normal flora... microorganisms that live on body surfaces and protect a host from harm. Ex--- intestinal flora provide vitamins for host; aid in digestion of foods; autotrophic bacteria in marine animals (algae in jellyfish); luminescent bacteria (nocturnal or deep water fish)

Antagonism --- occurs when one organism harms the other one. Sometimes end products of microbial metabolism can prove toxic to its host. Antagonism between microbes can help a host however, as in the case of normal flora -- which compete with harmful bacteria and rob the bad guys of nutrients and space by growing faster or producing products (bacteriocins) that harm the pathogens.

When a much larger host is invaded by a smaller one, the antagonistic relationship is call parasitism.

Many plants are destroyed by antagonistic relationships with microbes. (Think about a vegetable garden; rose mildew, etc.) And then... the classic microbe/host antagonistic response: disease.

Next time, we will begin to look at the intricately woven web of host and parasite interaction... and the pathogens of the microbial world.

4. Conclusion: So... how have Bacteria affected Earth’s History? Let’s review with the series of cartoons you have... (handout)

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