Introduction to Bacteria

Bacteria:

Bacteria Microorganisms

Objectives:

Objectives List seven differences between bacteria and eukaryotic cells. Describe three different ways bacteria can obtain energy. Describe the external and internal structure of Escherichia coli. Distinguish two ways that bacteria can cause disease. Identify three ways that bacteria can benefit humans.

Bacterial Structure:

Bacterial Structure Internal compartmentalization: Bacteria lack a cell nucleus or any other membrane bound internal structures. Cell Size: Bacteria tend to be smaller than eukaryotic cells (with a few exceptions). Multicellularity: Bacterial can only be single cell organisms while eukaryotes can have many cells. Chromosomes: Bacterial chromosomes consist of a single strand of DNA coiled into a circle. Eukaryotic chromosomes are linear pieces.

Bacterial Structure:

Bacterial Structure Reproduction: Bacteria only reproduce by binary fission. No mitosis is performed. Flagella: Bacterial flagella are simple structures composed of a single fiber of protein that spins like a corkscrew to move the organism. Eukaryotic flagella are more complex structures made of microtubules that whip back and forth. Some bacteria have short hair-like structures called pilli that allow them to stick to surfaces. Metabolic Diversity: Bacteria have many metabolic abilities that Eukaryotes lack. Bacteria, for example, can perform several types of aerobic and anaerobic processes while Eukaryotes tend to be strictly aerobic.

Bacterial Shapes:

Bacterial Shapes There are three types of bacterial shapes: Bacillus: Rod shaped cells. Coccus : Round or spherical cells. Spirillum : Spiral cells. Some bacteria associate into colonies of individual cells that are stuck together. For example, cells that group into lines or strings, called filaments, are referred to as strepto - while bacterial that group into clusters or clumps are called staphylo -

Bacterial Shapes:

Bacterial Shapes

Eubacteria vs. Archeobacteria:

Eubacteria vs. Archeobacteria Members of the kingdom Eubacteria have cell membranes made out of peptidoglycan , a network of polysaccharide (complex sugar) molecules linked by chains of amino acids. Many have a cell wall, and out of that, a gel like capsule. Members of Archeobacteria usually do not have a cell wall.

Cell Walls Among Eubacteria:

Cell Walls Among Eubacteria In Eubacteria there are two types of cell walls and they can be distinguished by staining under a microscope. One group is called Gram-negative and the other is called Gram-positive. It is important to know how to determine the difference because gram-staining tells us which antibiotics are effective against the bacteria we are investigating. Antibiotics: Chemicals that interfere with the life process of bacteria. Gram staining is the application of a crystal violet dye to a culture of bacteria. Bacteria that retain the color of the dye are called Gram positive ; bacteria that don't are Gram negative . The diagram to the right shows Gram-positive Staph aureus at the top and Gram-negative Pseudomonas aeruginosa at the bottom.

Endospores:

Endospores Bacteria often form thick-walled protective structures called endospores when conditions are not favorable for their survival. This condition allows them to survive for a time in an environment that would not ordinarily be suitable. When good conditions come along again, the bacteria emerges from its endospore .

Obtaining Energy:

Obtaining Energy All bacteria require energy but many receive it in different ways. Photosynthesizers : Bacteria that acquire energy from the sun using a variation of the photosynthesis reaction. Bacteria are divided by the color of pigments they contain and what chemical they use as a source of electron energy. Some use water like plants to gain electrons to power photosynthesis. Others use sulfer compounds. These tend to be anaerobic in nature.

Chemoautotrophs:

Chemoautotrophs Chemoautotrophs use chemical energy to survive and reproduce. These are often found in areas where sunlight can not reach. They are usually found in environments of high heat or chemical concentration. They can use chemicals like ammonia or methane to power their metabolism. Many around found in the soil and they play an important role in the nitrogen cycle.

Heterotrophs:

Heterotrophs Many bacteria break down other organisms to provide the raw materials they need. We call these bacteria decomposers. Along with fungi, these bacteria power the decay process that returns raw materials from dead animals and plants to nature to be reused.