The unseen multitudes
Did a friend even mention that you are nearly 1/1000 of mile tall? Probably not. What would be the point of measuring people in units as big as miles? Yet we think this way, in reverse, when we measure microorganisms. These are mostly single-celled organisms too small to be seen without a microscope.
Of all organisms, bacteria generally are the smallest. To be sure, viruses are smaller. We measure them in nanometers (billionths of a meter). But viruses are not living things. We consider them here because they infect just about every kind of organism in the great spectrum of life.
1. Bacteria are microscopically small, single-celled prokaryotic organisms. They do not have a profusion of internal, membrane-bound organelles in the cytoplasm, as eukaryotic cells do. Yet bacteria show great metabolic diversity, and many make complex behavioral responses to the environment.
2. Today there are two great bacterial lineages, the archaebacteria and dubacteria. Archaebacteria live in such inhospitable, anaerobic habitats that they may resemble the first living cells on earth. Most bacterial species are eubacteria, which inhabit nearly all existing environments.
3. Bacteria reproduce by binary fission, a cell division mechanism that immediately follows DBA replication and that divides the parent cell into two genetically equivalent daughter cells.
4. Nearly all viral multiplication cycles include five steps: attachment to a suitable host cell, penetration, viral DNA or RNA replication and protein synthesis, assembly of new viral particles, and release from the infected cell.
Did a friend even mention that you are nearly 1/1000 of mile tall? Probably not. What would be the point of measuring people in units as big as miles? Yet we think this way, in reverse, when we measure microorganisms. These are mostly single-celled organisms too small to be seen without a microscope.
Of all organisms, bacteria generally are the smallest. To be sure, viruses are smaller. We measure them in nanometers (billionths of a meter). But viruses are not living things. We consider them here because they infect just about every kind of organism in the great spectrum of life.
1. Bacteria are microscopically small, single-celled prokaryotic organisms. They do not have a profusion of internal, membrane-bound organelles in the cytoplasm, as eukaryotic cells do. Yet bacteria show great metabolic diversity, and many make complex behavioral responses to the environment.
2. Today there are two great bacterial lineages, the archaebacteria and dubacteria. Archaebacteria live in such inhospitable, anaerobic habitats that they may resemble the first living cells on earth. Most bacterial species are eubacteria, which inhabit nearly all existing environments.
3. Bacteria reproduce by binary fission, a cell division mechanism that immediately follows DBA replication and that divides the parent cell into two genetically equivalent daughter cells.
4. Nearly all viral multiplication cycles include five steps: attachment to a suitable host cell, penetration, viral DNA or RNA replication and protein synthesis, assembly of new viral particles, and release from the infected cell.
1 comment:
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