Environmental Microbiology

"In the year 1657 I discovered very small living creatures in rain water."

Antonie van Leeuwenhoek

Dutch Scientist and Inventor

Microorganisms

• Microorganisms play an important role in the natural environment and in engineered systems. In addition, they are important in the transmission of many diseases. Thus, their understanding is critical to medicine, environmental science and environmental engineering.
• Microorganisms are present in all natural waters.
  • Microorganisms pose the threat of disease when humans use a contaminated water source or contact the infectious organisms in other ways.
  • Potable water systems are designed to kill or inactivate pathogenic organisms.
• In the natural environment they serve the beneficial task of decomposing wastes.

• Within engineered systems, microorganisms are a critical part of all municipal and many industrial wastewater treatment processes.
  • In engineered treatment systems, microorganisms convert waste products to nutrients and minerals, lessening the impact on the environment.
• Microorganisms are an integral part of many food and beverage production processes.
  • Dairy products such as cheese and yogurt
  • Beverages such as wine, and beer
• Pathogenic microorganisms are also of concern to the food and beverage industry.
• Microorganisms are important in the production of many medical drugs.
• Many microorganisms serve a beneficial function, others are harmful, as pathogenic or disease causing organisms.
• Microorganisms include viruses, bacteria, algae, fungi, protozoa, and rotifers.

Microorganisms are Ubiquitous

• They are present in almost every imaginable place on Earth
  • In the soil, in the air, at the bottom of the ocean, and on and in other life forms, including humans.

Discovery

• The first known recorded observations of microorganisms were by Dutch linen merchant, and amateur scientist, Antonie van Leeuwenhoek, in 1673.
  • Leeuwenhoek used a simple single lens microscope for his observations.
  • He sent detailed sketches of microorganisms with descriptive letters to the Royal Society of London, many of which were translated and published. At this time microorganisms were not connected with disease, they were simply small creatures of interest

Microorganisms and Disease

• It was not until some 200 years later, in 1876, that Robert Koch, a German physician, proved the connection between infection and microorganisms with Bacillus anthracis (anthrax).
  • He observed that B. anthracis, a particularly large bacterium, was always present in the blood of cattle with anthrax.
  • But, did the organism cause the disease or did the disease cause the organism? He took blood from an infected animal and injected a small amount of it into a healthy animal. The healthy animal then contracted anthrax. He repeated this procedure twenty times. Each time the newly inoculated animal contracted anthrax. He even grew B. anthracis on culture plates. This was then inoculated into a healthy animal. Each time the animal contracted anthrax. Thus, Koch proved the germ theory of disease.
• Twenty years before Kock proved the germ theory, a British physician and public health official, John Snow linked cholera to a contaminated water supply in London, England. In south London, two competing water companies supplied water to customers. They were Southwark and Vauxhall which obtained its water in central London from the Thames River, and Lambeth which obtained its water from the Thames as well, but far upstream of London. In some areas, both had water mains and customers had a choice. In other sections, some areas had one company, other areas the other company. In 1855 there was no water treatment or disinfection. Through an extensive 7 week investigation, Show was able to determine that the death rate for those using the Southwark and Vauxhall water had a death rate of 315 per 10,000 people. The Lambeth water users had a death rate of only 37 per 10,000 users during that 7 week period.
• Smallpox was the first major disease to be eradicated. Its eradication is the result of a very effective attenuated vaccine which was used throughout the world. The developed nations were the first to eradicate the disease. North America was smallpox free by the end of the 1960s. In 1966 the World Health Assembly and the World Health Organization began a coordinated effort to eradicate the disease from Earth. In 1980, the World Health Assembly announced that Earth was smallpox free. The two remaining smallpox virus stocks, held in the CDC in Atlanta and a research facility in the Russian Federation, are scheduled for destruction in 1999. If this occurs, it will be the first intentional destruction of a species.

Classification

• Prokaryotic organisms are single cell organisms, including only bacteria, which do not have a nuclear membrane Eukaryotic microorganisms may be single or multicellular and do contain a nuclear membrane. These include:
  • algae, fungi, protozoa, and rotifers.
  • Viruses are grouped separately.

Bacteria

• Bacteria are unicellular organisms which do not have a nuclear membrane. Bacteria vary in size from 0.1 µm to more than 5 µm. Their shape varies from cylindrical to spherical. The common Escherichia coli is 0.5 µm in diameter and 2 µm long. Bacteria are comprised of a cell wall, cell membrane, cytoplasm, and DNA The nuclear material, a single strand of DNA, contains the genetic information of the cell. The cell wall provides the structural integrity for the bacterium.
  • The cell membrane selectively allows passage of nutrients into the cell and waste out of the cell.
  • The cytoplasm is composed of different organic and inorganic molecules necessary for cell function.
  • Within the cytoplasm are thousands of ribosomes which translate the genetic code and produce cell proteins.

• Many bacteria have a means of motion, flagella.
  • Flagella are single strands of a hollow protein which the bacteria is able to rotate, producing motion.
  • The speed that bacteria are able to achieve with their flagella is about 20 to 80 µm/s, or about 10 cell lengths per second.
  • In contrast, Olympic sprinters can attain speeds of approximately 10 m/s, or 5 body lengths per second.
• Bacteria exist in many locations inhospitable to most other organisms.
  • the interface between water and fuel in hydrocarbon fuel tanks
  • the depths of the oceans where hot waters escape from fissures
  • the mouth and teeth of mammals, including humans
  • in and on our foods, and our water supplies
  • in the intestinal tract of mammals
  • they are ubiquitous

Viruses

• Viruses are the simplest form of life known. (Some scientists do not consider them a life form.) They exist in two forms,
  • infectious virus particles which contain DNA or RNA, a structural coat, and possibly some other chemicals. And,
  • as a part of a host cell's DNA or RNA.
• The structure of a virion.

• The virion particle contains
  • nucleic acid, and
  • a capsule or nucleocapsid, composed of capsomere units.
  • Some viruses also contain a coating surrounding the nucleocapsid, termed an envelope.
• When a virus infects a host, the nucleocapsid attaches to the host cell wall and the nucleic acid is injected into the cell. The nucleic acid then integrates into the host's nucleic acid.
• Viruses infect many different life forms: plants, bacteria, mammals.

Algae

• Algae are chlorophyll containing eukaryotic organisms which carry out oxygenic photosynthesis.
  • Most are microscopic
  • Some, such as kelp, reach lengths of over 100 feet.
  • Photosynthetic activity occurs in membranous structures, chloroplasts, which are contained within the cell.

• Although algae utilize carbon dioxide and produce oxygen in the light, they concurrently respire, consuming oxygen and producing carbon dioxide.
• During periods of light, the net effect is production of oxygen.
  • Algal photosynthetic production of oxygen far exceeds respiratory consumption of oxygen in the presence of light.
  • However, during periods of darkness, the respiration continues, without the photosynthesis. During this period, algae consume oxygen.
• Algae are important to the environment for multiple reasons.
  • Algae are at least partially responsible for taste and odor problems in public drinking water supplies which originate in surface waters, particularly lakes.
  • Algae are responsible for much of the suspended matter which is present in the effluent from lagoon wastewater treatment systems.
  • Algae are produced where wastewaters or farm runoff results in the addition of excessive amounts of nitrogen and phosphorus to surface waters.
  • Algae are important in the environment as primary producers of biomass.
  • Marine phytoplankton, algae, are responsible for approximately 90 percent of the photosynthesis on Earth.

Protozoa

• Protozoa are important primarily due to their infectious nature and their role in the mixed microbial cultures of wastewater treatment systems.
  • Many protozoa are parasitic to humans and are thus of importance in water treatment and human health.
  • Other protozoa are important because they consume large amounts of bacteria, helping to clarify wastewater.
  • Protozoa are much larger than bacteria. Due to their predatory nature, most are motile. There are several forms of protozoa.
  • Flagellated protozoa have one or more flagella for motility.
  • Ciliated protozoa have cilia covering the cell membrane which are used for motility.
  • Another common form of protozoa are the amoebas, a group which is characterized by a flowing movement.

Chemicals of Life

Nutrients required for biosynthesis.

Diseases and Disease Transmission

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