Earth Science: Microorganisms – Bacteria
Bacteria are cellular organisms without a nucleus from the group prokaryotes. Prokaryotic cells are much smaller compared to eukaryotic cells, which contain a nucleus and several chromosomes.
Bacteria are so tiny that they are invisible to the human eye, yet they can significantly impact the environment and lifestyle of other organisms.
Biology – Microorganisms – Structure and Metabolism of Bacteria
Most bacteria are just a few micrometers in size, observable only using a microscope. So naturally, it was the microscope builder Antoni van Leeuwenhoek who discovered bacteria during the 17th century.
Bacteria are typically spherical or rod-shaped. Some species consist of helical cells and others form thread-like out- growths similar to mushroom filaments. Their size is normally between two and five micrometers (ujm); in exceptional cases, bacteria may reach a length of 50 ) ujm or even more. Bacterial cells lack nuclei as well as organelles that are typical for eukaryotic cells.
Their cell walls usually consist of a rigid structure made of polysaccharide and amino acid molecules. If the cell wall is thin with a single layer the bacteria are considered gram-negative and if the cell wall is a thick multilayered mesh, then the bacteria are considered gram-positive. Reproduction normally occurs by division.
Some species have flagellae and are therefore mobile. Other bacteria produce endospores which is a dormant structure within the organism that allows survival for many years, even during unfavorable conditions.
Metabolic diversity
Different bacteria take various approaches to the production of energy. Most species use organic matter, especially carbohydrates. Certain species, however, can also generate energy from inorganic matter, such as sulfate compounds. Some bacteria use sunlight for energy pro- duction while others use the energy from chemical reactions.
Bacteria can also grow without oxygen or they may live parasitically or symbiotically without access to air circulation. Furthermore, some species thrive in comparatively high temperatures while others can tolerate high concentrations of salt. Due to their rich diversity, bacteria can be found in almost all environments.
Laboratory cultures
Due to the tiny size of bacteria, close examination in the environments where they are commonly found is very difficult. Therefore, it is easier to study them in a laboratory environment. Here, pure bacterial cultures are grown on an artificially made culture medium.
These can be liquid cultures or solid agars. In order to identify pathogens, it is also common practice to first set up a growth environment for a pure culture.
BASICS
IF CONDITIONS are favorable, bacteria can multiply rapidly In extreme cases, they double every 11 minutes. After only one hour, they could weigh about 5,000 tons.