Bacteria Power Point

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Presentation Transcript

Slide 1: 

The World of Bacteria Characteristics Shape Movement Reproduction

Slide 2: 

Bacteria • Most microorganisms are prokaryotes – single celled organisms that lack a nucleus. – Prokaryotes can be divided into two very different kingdoms: –Eubacteria. –Archaebacteria. • Bacteria represent the most ancient groups on Earth. They have adapted to almost every environment, and they have evolved more ways to obtain nutrients than all eukaryotic organisms combined. All bacteria: • Are unicellular. • Lack a cell nuclei. • Lack membrane bound organelles.

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Eubacteria Peptidoglycan Cell wall Cell membrane Ribosome Pili DNA Flagellum Larger (in number) kingdom. • Live almost everywhere” – Land, fresh water, ocean, in the human body. • Surrounded by a cell wall for protection and determination of shape. • May also contain a 2nd cell membrane outside of the wall.

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Archaebacteria Look very similar to eubacteria, but are very different chemically. – Lack the peptidoglycan of eubacteria. – Have different membrane lipids than eubacteria. • DNA sequence of archaebacteria is more like those of eukaryotes. – Based on DNA evidence, scientists have suggested that archaebacteria may be the ancestors of eukaryotes. • Tend to live in extremely harsh environments – such as oxygen free environments or extremely salty environments.

Slide 5: 

Bacteria Shape Bacteria come in three shapes: – Spherical-shaped or cocci (Strep) – Rod-shaped or bacilli (E-Coli) – Spiral-shaped or spirilla (Leptrospira)

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• Bacteria have an inner cell membrane made of lipids and an outer cell wall made of polysaccharides. (See Diagram A) • Some bacteria have a 3rd layer – a cell membrane outside of the cell wall made up of polysaccharides that are bound to lipids. (See Diagram B) Bacterial Cell Walls 3rd Outer Membrane Cell Wall Membrane

Slide 7: 

Some bacteria do not move. • Others are propelled by flagella or whip like structures. • Some lash, snake, or spiral forward. • Others glide along the slime they produce. Movement

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• Heterotrophs - organisms that cannot make their own food. – Most bacteria fall in this category. – Many feed on dead plants, fallen leaves, dead animals, petroleum, pesticides, nylon and other industrial products. • Autotrophs - organisms that make their own food. – Some bacteria can use light energy to produce food – photoautotrophs. – Other bacteria use chemicals such as ammonia, or sulfur, to produce energy - chemoautotrophs. Metabolic Diversity

Slide 9: 

• When conditions are favorable (correct temperature, ample food and space), some bacteria can divide as often as every 20 minutes. – Binary Fission – when a bacterium doubles in size, replicates its DNA and divides in half. – Genetic information is not exchanged or recombined. – Form of asexual reproduction. – Conjugation – when some genetic material is transferred to another bacteria cell. – does not result in more bacteria. – does provide for genetic variation. – Spore Formation – when conditions become unfavorable, many bacteria form spores and remain dormant until conditions become more favorable. Growth & Reproduction