![]() Such dormancy phenotypes can display various degrees of tolerance to antibiotics and therefore a detailed understanding of these phenotypes is crucial for combatting chronic infections and associated diseases. Morphological changes may also be associated with specific physiological phenotypes such as the formation of dormant or persister cells in a “viable but non-culturable” (VBNC) state which frequently display different shapes and size compared to their active counterparts. 2Shell International Exploration & Production Inc., Westhollow Technology Center, Houston, TX, United Statesīacteria modify their morphology in response to various factors including growth stage, nutrient availability, predation, motility and long-term survival strategies.1Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom. ![]() Groenhof 1 Sariqa Wagley 1 Ping Liu 2 David A. Eukaryotes are colored red, archaea green and bacteria blue.Ann L. Figure: Archaea and other domains: Phylogenetic tree showing the relationship between the Archaea and other domains of life. It should be noted that Bacteria and Archaea are similar physically, but have different ancestral origins as determined by DNA of the genomes that encode different prokaryotes. The archaea and eukaryotes are more closely related to each other than either is to the bacteria. However, molecular systematics show prokaryotic life to consist of two separate domains, originally called Eubacteria and Archaebacteria, but now called Bacteria and Archaea that evolved independently from an ancient common ancestor. The term “bacteria” was traditionally applied to all microscopic, single-cell prokaryotes, having the similar traits outlined above. Small size is extremely important because it allows for a large surface area-to-volume ratio which allows for rapid uptake and intracellular distribution of nutrients and excretion of wastes. For example, Escherichia coli cells, an “average” sized bacterium, are about 2 micrometres (μm) long and 0.5 μm in diameter. Perhaps the most obvious structural characteristic of bacteria is (with some exceptions) their small size. Figure: Binary fission: Many bacteria reproduce through binary fission. Bacteria grow to a fixed size and then reproduce through binary fission, a form of asexual reproduction. Unlike in multicellular organisms, increases in cell size (cell growth and reproduction by cell division) are tightly linked in unicellular organisms. Figure: Bacterial structures: Cell structure of a Gram-positive prokaryote. These subcellular compartments have been called “bacterial hyperstructures”. Bacteria were once seen as simple bags of cytoplasm, but elements such as prokaryotic cytoskeleton, and the localization of proteins to specific locations within the cytoplasm have been found to show levels of complexity. They consequently lack a true nucleus, mitochondria, chloroplasts, and the other organelles present in eukaryotic cells, such as the Golgi apparatus and endoplasmic reticulum.
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