Chapter 4 A Survey of Prokaryotic Cells and Microorganisms (Sections 4.5-4.7)

What are vibrios and coccobacilli?

A vibrio is a gently curved rod shaped bacteria. A coccobacilli is a short and plump rod shaped bacteria. Both are considered genus Bacilli.

Explain the characteristics of archaea that indicate that they constitute a unique domain of living things that is neither bacterial or eukaryotic.

Archaea are prokaryotic in general structure and share many other bacterial structures. Their genetic sequences are also only found in their RNA. Their cell walls are composed of polysaccharides or protein. They lack peptidoglycan and some do not have any cell walls.

Explain some of the ways species level in bacteria is defined, and name at least three ways bacteria are classified below the species level.

Bacterial species are not defined like animals or plants, which can be easily organized by producing viable offspring when mating with others of its own kind. Instead, bacteria species are organized as a collection of all bacterial cells which share a pattern of similar traits. Bacteria below the species level are categorized by subcategories. The three sub categories are subspecies, strain, and type.

Discuss several ways in which bacteria are medically and ecologically important.

Cyanobacteria, are the one of the oldest organisms on earth, they are thought to be the first photo-synthesizers and are responsible for converting the atmosphere from anaerobic to aerobic. Medically, there are obligate intracellular parasites which reside in host cells and cannot function without a host.

What general characteristics are used to classify bacteria?

In general, the level of genus and species are used to classify bacteria based on the morphology, bacterial physiology, serological analysis, and genetic techniques. This is all facilitated by using special technologies.

What are the most useful characteristics for categorizing bacteria into phyla?

Phylum Firmicutes are mostly gram positive bacteria that have low Guanine and Cytosine composition. Phylum Actinobacteria are mostly gram positive bacteria that have a high Guanine and Cytosine composition. Other Phyla are organized based on being gram negative, but otherwise are widely varied, these include: Phylum Chlaymdiae reproduce inside host cells and are among the smallest bacteria Phylum Spirochetes move their slender twisted cells by periplasmic flagella Phylum Planctomycetes live in freshwater and reproduce by budding. Phylum Bacteriodetes are mostly anaerobic rods that are found in intestinal tracts of animals and in soil ,water and rock sediments.

Describe pleomorphism, and give examples of bacteria with this trait.

Pleomorphism is when cells of a single bacterial species show different appearance in size, shape and color when observed. This is caused by individual variations in cell wall structure caused by nutritional and hereditary differences. Bacteria with this trait include: Corynebacterium diphtheria and Mycoplasmas.

How are spirochetes and spirilla different?

Spirilla have a helix shaped form, while the Spirochetes are more flexible in their form and are shaped like a spring.

Describe the three major archaeal lifestyles and adaptations to extreme habitats.

The first major lifestyle is the Methanogens. These archaea convert CO2 and H2 into methane gas (CH4). They are commonly found in anaerobic mud and at the bottom sediments of lakes and oceans. The second major lifestyle is the extreme halophiles. These require salt to grow and have a high salt tolerance. They exist in the saltiest places on earth such as salt mines and salt lakes. The third major lifestyle are the psychrophiles and the hyperthermophiles. These both live in extreme temperatures on earth. The psychrophiles live in very cold temperatures, while the hyperthermophiles live in extremely high temperatures.

What is the difference between the use of the shape bacillus and the name Bacillus?

The shape bacillus is a cell that is cylindrical, while the name Bacillus is a genus named for its rod shape.

Rank the size ranges of bacteria according to shape, and compare bacterial size with viruses and eukaryotic cells.

The sizes of bacteria range from those just barely visible with a light microscope (0.2 um microns) to those measuring a thousand times that size. Cocci measure from 0.3-3.0 um in diameter. Bacilli measure from 0.2-2.0 um in diameter and are 0.5-20 um in length. Viruses are much smaller and are measured in nm (nano meters). Eukaryotic cells are much larger.

Classify Bacteria According to their Basic Shapes

The three basic shapes of bacteria are Cocci, Bacilli, and Spirilla. Cocci (Coccus) are spherical or ball shaped bacteria. They can be perfect spheres or oval shaped. Bacilli (Bacillus) are rod shaped cylindrical bacteria that are longer than they are wider. Spirilla (Spirillum) are cylindrical shaped bacteria that have a spiral shaped helix that is twisted like a corkscrew.

Name two main groups of obligate intracellular parasitic bacteria and explain why these groups cant live independently.

The two main groups of obligate intracellular parasites are Rickettias and Chlamydias. These groups cannot multiply outside of a host cell and cannot carry out metabolism completely on their own.

What is meant by the terms extremophile and hyperextremophile?

These are terms that mean that the archaea 'love' the most extreme habitats on earth to live.