Domain Bacteria Research Paper Example | Topics and Well Written Essays - 500 words

Domain Bacteria - Research Paper Example The relatedness between any two given metazoans such as a human and a slug is often much more than the relation between two bacteria species. They appear in a variety of shapes (rods, spirals, spheres, blogs and helical among others) and sizes ranging between 0.5 and 5.0 microns. Most bacteria are of one of three typical shapes, which include round/ball-shaped (coccus), rod-shaped (bacillus) and spiral-shaped (spirillum), with an additional group, vibrios, that appear as incomplete spirals. Scientists also characterize bacteria by their growth patterns such as the chains formed by streptococci. While some bacteria, mainly the spirillum and bacillus forms, are motile or swim about by whip-like movements of flagella, others have pili, rigid rod-like protuberances, which serve as tethers. Pili join pairs of bacteria together facilitating transfer of DNA between them. Some bacteria have short, hair-like, proteinaceous projections called fimbriae at the cell ends or over the entire surface, which enable the bacteria to adhere to surfaces. Depending on the bacteria species, flagella may be set in any of four ways, which includes the monotrichous form with a single flagellum at one end, the amphitrichous with a single flagellum at each bacterium end, the lophotrichous with two or more flagella at either or both bacterium ends and the peritrichous form with flagella distributed over the entire cell. Bacterial cells can exist as discrete individual cells or may group together in chains as in the case of rods and cocci. Cocci forms can also aggregate in clusters. They contain a cell envelope comprising of a capsule, the cell wall and a plasma lemma or plasma membrane and a cytoplasmic region, which contains the cell genome, ribosomes and various cell inclusions. Most bacteria have a rigid cell wall, which consists of a polymer of disaccharides that are cross-linked by peptides (short amino acid chains) forming a