A cell is the fundamental structural unit of all living things. All cells have a surrounding membrane and an internal, water-rich substance called the cytoplasm. A more or less typical bacterium is comparatively much simpler than a typical eukaryotic cell. Within the eukaryotic cell is genetic material, deoxyribonucleic acid (DNA), and organelles. DNA, combined with protein, is organized inside the nucleus into structural units called chromosomes. Cells are made mostly of organic compounds such as proteins, nucleic acids, lipids, and carbohydrates. Water makes up 60 to 65 percent of the cell.

Bacteria lack the membrane-bound nuclei of eukaryotes; their DNA forms a tangle known as a nucleoid, but there is no membrane around the nucleoid, and the DNA is not bound to proteins as it is in eukaryotes. Whereas eukaryote DNA is organized into linear pieces, the chromosomes, bacterial DNA forms loop

The other group, autotroph, fix carbon dioxide to make their own food source; this may be fueled by light energy (photoautotrophic), or by oxidation of nitrogen, sulfur, or other elements (chemoautotrophic). While chemoautotrophs are uncommon, photoautotrophs are common and quite diverse. They include the cyanobacteria, green sulfur bacteria, purple sulfur bacteria, and purple nonsulfur bacteria. The sulfur bacteria are particularly interesting, since they use hydrogen sulfide as hydrogen donor, instead of water like most other photosynthetic organisms, including cyanobacteria.

The cell membrane is surrounded by a cell wall in all bacteria except one group, the Mollicutes, which includes pathogens such as the mycoplasmas. The composition of the cell wall varies among species and is an important character for identifying and classifying bacteria. Bacteria have a fairly thick cell walls made of peptidoglycan (carbohydrate polymers cross-linked by proteins); such bacteria retain a purple color when stained with a dye known as crystal violet, and are known as Gram-positive (after the Danish bacteriologist who developed this staining procedure). Other bacteria have double cell walls, with a thin inner wall of peptidoglycan and an outer wall of carbohydrates, proteins, and lipids. Such bacteria do not stain purple with crystal violet and are known as Gram-negative.

When most people think of bacteria, they think of disease-causing organisms, like the Streptococcus bacteria, which are known to cause strep throat. While pathogenic bacteria are notorious for such diseases as cholera, tuberculosis, botulism and gonorrhea, such disease-causing species are a comp

Some common words found in the essay are:
Gram-positive Danish, , Nostoc Spirulina, carbon dioxide, sulfur bacteria, grow bacteria, sulfur bacteria purple, gaseous nitrogen, source energy, bacteria purple, crystal violet, makes bacteria, nitrogen sulfur, cell wall,
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Approximate Pages = 4 (250 words per page double spaced)