Bacteria Created by: Jen Fritz Sarah Baker Kristen Nelson
Linnaean Hierarchy • Domain • Bacteria • Kingdom • Prokaryotes
Systematics • Scientists use a variety of ways to classify bacteria: • Where they live • Depend on oxygen • Their shape • Source of carbon • Gram-positive and gram-negative
Classify Divided into three major groups: • Thermoacidophiles –live in highly acidic and hot environments. • Halophiles- live in highly saline environments. • Methanogens –produce methane, they live in the intestines of animals and such harsh places as undersea hydrothermal vents.
CLASSIFICATION • Split up into 3 groups based on their response to gaseous oxygen • Aerobic—thrive in the presence of oxygen and require it to survive • Anaerobic—cannot endure gaseous oxygen • Facultative anaerobes—prefer growing in the presence of oxygen, but can grow without it
CLASSIFICATION • Classified by how they obtain their energy • Heterotrophs—derive energy from breaking down complex organic compounds that they must take in from the environment • Grow within another living cell and use the nutrients of the host cell • Autotrophs—fix carbon dioxide to make their own food • Use light energy or oxidation of nitrogen, sulfur, or other elements
Classification • Classified based on shape • Rod-shaped • Spherical cocci • Spiral-shaped spirilla • Largest of the 3 types and the easiest to identify
CLASSIFICATION • First classification scheme was developed by Hans Christian Gram using the Gram stain • Separates bacteria based on the structural characteristics of their cell walls • Gracilicutes - Gram negative staining bacteria with a second cell membrane • Firmicutes - Gram positive staining bacteria with a thick peptidoglycan wall • Mollicutes - Gram negative staining bacteria with no cell wall or second membrane • Mendosicutes - atypically staining strains now known to belong to the Archaea
Key Characteristics • in classifying bacteria: • photosynthetic or nonphotosynthetic • motile or nonmotile • Unicellular, colony-forming or filamentous • formation of spores or division by transverse binary fission
BODY • capsule, the cell wall, the cell membrane, cytoplasm • No intracellular organelles (no mitochondria and chloroplasts) • Unicellular organisms • Pili—hollow, hair like structures made of protein allow bacteria to attach to other cells • Flagella—long appendages which rotate by means of a “motor” • average most species of bacteria have diameters of 0.5 to 2.0 microns • Contain plasmids, small loops of DNA, that can be transmitted from one cell to another • This makes bacteria adaptable • Biologists can insert new genes into bacteria easily b/c of plasmids
Where theylive • They are found nearly everywhere • Prokaryotic cells and fossils have been found in almost every conceivable environment on the earth • hot sulfur springs to beneath the ocean floor and within larger cells • They hold all the records for living in the coldest, hottest, most acidic and most highly pressurized environments. • under glaciers • floating around in clouds • miles down on the sea floor • at temperatures greater than 100 C • Never find one bacteria on its own. They tend to live together in clumps, chains or planes
Obtain Food • Prokaryotes use 4 major nutritional modes to obtain food. These modes are: • Photoautotrophs: these use CO2 as a carbon source, and light for energy. e.g., photosynthesis • Photoheterotrophs: these use light as an energy source but must ingest pre-made organic compounds. This mode is very rare. • Chemoautotrophs: These use CO2 as a carbon source, but obtain their energy from inorganic molecules such as hydrogen sulfide. • Chemoheterotrophs: These obtain both their energy and carbon from organic compounds. We are chemoheterotrophs.
Growth and Reproduction • asexual reproduction (one parent) binary fission • Inherit identical copy of their parent’s genes • Have the ability to evolve and change their genetic material • Three techniques of reproduction (genetic transfer) exhibited by prokaryotes include: • (a) transformation - genes are taken up from the surrounding environment. • (b) conjugation - genes are transferred directly from one prokaryote to another. • (c) transduction - genes are transferred by viruses.
Important roles • Decomposers: • Organic carbon, in the form of dead and rotting organisms, would quickly deplete the carbon dioxide in the atmosphere if not for the activity of decomposers • organisms die & the carbon contained in their tissues becomes unavailable for most other living things. Decomposition is the breakdown of these organisms, and the release of nutrients back into the environment.
Important roles • Plants rely on nitrogen from the soil for their health and growth, and cannot acquire it from the gaseous nitrogen in the atmosphere. • The primary way in which nitrogen becomes available to them is through nitrogenfixation by bacteria
Important Roles • decomposition of dead organisms, • chemical fixation • symbiotic relationships (such as that between nitrogen-fixing bacteria and plant roots) • Many prokaryotes can “fix” nitrogen. This means they can convert atmospheric nitrogen gas (N2) into ammonia, a form useable by other bacteria and plants. This process is called nitrogen fixation. • Many animals are completely dependent on bacteria to digest their food for them, particularly herbivores, large vertebrates like cows and sheep, to small invertebrates like termites all are dependant on bacteria • some bacteria also play an important role in trapping the suns energy so that it can be used by living organisms
Impact • making soil • degrading pollutants such as oil and plastics • fermented foods such as cheese, pickles, soy sauce, sauerkraut, vinegar, wine, and yogurt. • genetic engineering improvements in agricultural crops • commercial production of pharmaceuticals • Any cycle or system you look at has bacteria playing a crucial supportive role in it somewhere. Bacteria are an essential in the maintenance of these flows of energy and nutrients throughout our world. Without them the whole ecosystem would collapse. • Most of these bacteria live within us, harmlessly going about their short lives without causing us any problems at all. some in fact may even be beneficial
Cons of Bacteria • Diseases caused by bacteria: • Tuberculosis • Cholera • Leprosy • tetanus • bacterial pneumonia • whooping cough • Lyme disease • Gonorrhea • syphilis • Chlamydia. • bioterrorism • Some bacteria attack us in a manner that is not immediately painful in fact the pain may not be apparent for years. The primary example of this is tooth decay
For Your Pleasure • First bacteria was observed by Anton Van Leeuwenhoek in 1674 • Oldest bacteria fossil record is 3.5 billion years old • It is possible for bacteria to reproduce as often as every 20 minutes • They are the most abundant of all organisms • evolution of the prokaryotic cell has been fairly dormant over its two billion year lifespan.
For Your Pleasure Cnt’d… • About 5000 different kinds of prokaryotes are currently recognized • during the year 2000, bacterial diseases likely killed 5 million people which accounts for 10% of the 52 million human deaths occurring on average every year • billions of individual bacteria are living in and on most of us most of the time.