CHARACTERISTS OF MIROORGANISMS
Microbiology are the smallest organisms on Earth. In fact, the term microorganism literally means "microscopic organism." Microorganisms may be composed of prokaryotic or eukaryotic cells, and they may be single-celled or multicellular. Examples of microorganisms include algae, fungi, protozoa, bacteria and viruses. Prokaryotic microorganisms is prokaryotes arguably represent the earliest forms of life on Earth. They are broken up into two categories which are bacteria and archaea. A prokaryotic cell lacks a nucleus to hold the cell's DNA and lacks any sort of organized packaging or housing to hold the rest of the cell's machinery. Because prokaryotic cells lack this extra material, they are almost always smaller than other cell types; all prokaryotes are microorganisms, and they are almost single-celled. Eukaryotic cells are larger and more complex than prokaryotic cells. The DNA of a eukaryotic cell is neatly packaged within its nucleus, and there are several different structures that house the cellular machinery that can make eukaryotic microorganisms self-sufficient. The structures located in eukaryotic cells may include the endoplasmic reticulum, golgi apparatus, mitochondria, and ribosomes, as well as chloroplasts in photosynthetic cells. Examples of eukaryotic microorganisms include fungi, algae, protozoa and various microscopic parasitic worms.
Bacteria are individual living cells. Bacteria cells are similar to your cells in many ways; yet, they also have distinct differences. Bacteria have many unique adaptations allowing them to live in many different environments. Bacteria are so small that they can only be seen with a microscope. When viewed under the microscope, they have three distinct shapes. Bacteria can be indentified by their shape which are bacillus are rod-shaped, coccus are sphere-shaped and spirillius are spiral-shaped. Bacteria are like eukaryotic cells in that they have cytoplasm, ribosomes, and a plasma membrane. Features that distinguish a bacterial cell from a eukaryotic cell include the circular DNA of nucleoid, the lack of membrane-bound organelles, the cell wall of peptidoglycan, and flagella. Besides that, Protozoa are eukaryotic microorganisms. Although they are often studiedin zoology courses, they are considered part of the microbial world because they are unicellular and microscopic. Characteristics of Protozoa are they do not have cell wall; some however,possess a flexible layer, a pellicle, or a rigid shell of inorganic material outside the cell membrane. They have the ability during their entire life cycle or part of it to move by locomotor organelles or by a gliding mechanism. They have heterotrophic mode of nutrition, whereby the free-living forms ingest particulates, such as bacteria, yeast, and algae, while the parasitic forms derive nutrients from the body fluids of their hosts.
Moreover, Algae are eukaryotic organisms that have no roots, stems, or leaves but do have chlorophyll and other pigments for carrying out photosynthesis. Algae can be multicellular or unicellular. Cells are covered by a rigid cellulose cell wall. Algae are eukaryotic thallophytes and photoautotrophs. Algae reproduce either by vegetative, asexual or sexual method. Storage form of food in algae is starch. Algae are usually aquatic, either freshwater or marine and some are terrestrial. Furthermore, Fungi is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from the other eukaryotic life kingdoms of plants and animals. Characteristics of fungi are fungi have cell walls are composed mainly of a carbohydrate called chitin, while plant cell walls are composed mainly of cellulose. Fungi are achlorophyllous, which means they lack of chlorophyll pigments present in the chloroplasts in plant cells and which are necessary for photosynthesis. The carbohydrate molecule used to store nergy in fungi is glycogen. Fungi are heterotrophs, which means that they obtain nutrients by absorption. Hyphae can grow and form a network called a mycelium. A spore is a unit of asexual reproduction, specifically a reproductive cell surrounded by a thick cell wall. Yeasts are unicellular fungi that do not produce hyphae. Fungi can reproduce both sexually and asexually.
Lastly, Virus is a small infections agent that replicates only inside the living cells of other organisms. Viruses can infect all types of life forms, from animals and plants to mcroorganisms, including bacteria and archaea. Characteristics of viruses are enclosed in protective envelope. They have spikes, which helps them to attach to the host cell. Viruses are non cellular and do not respire, do not metabolize and do not grow but they do reproduce. They contain a protein coat called the capsid. They have a nucleic acid core containing DNA or RNA. Ribosome and enzymes are absent, which are needed for metabolism. Viruses are considered both as living and non living things, as viruses are inactive when they are present outside of host cells and are active in side of host cells.
Examples of Bacteria :
Examles of Protozoa:
Examples of Fungi :
Examples of Algae:
Examples of Viruses :
HISTORY OF MICROBIOLOGY
Historians are unsure who made the first observations of microorganisms, but the microscope was available during the mid-1600s, and an English scientist named Robert Hooke made key obsevations. He is reputed to have observed strands of fungi among the specimens of cells he viewed. In the 1670s and the decades thereafter, a Dutch merchant named Anton van Leeuwenhoek made careful observations of microscopic organisms, which he called animalcules. Until his death in 1723, van Leeuwenhoek revealed the microscopic world to scientists of the day and is regarded as one of the first to provide accurate descriptions of protozoa, fungi, and bacteria.
After van Leeuwenhoek died, the study of microbiology did not develop rapidly because microscopes were rare and the interest in microorganisms was not high. In those years, scientists debated the theory of spontaneous generation, which stated that microorganisms arise from lifeless matter such as beef broth. This theory was disputed by Francesco Redi, who showed that fly maggots do not arise from decaying meat (as others believed) if the meat is covered to prevent the entry of flies. An English cleric named John Needham advanced spontaneous generation, but Lazzaro Spallanzani disputed the theory by showing that boiled broth would not give rise to microscopic forms of life.
Louis Pasteur and the germ theory. Louis Pasteur worked in the middle and late 1800s. He performed numerous experiments to discover why wine and dairy product became sour, and he found that bacteria were to blame. Pasteur called attention to the important of microorganisms in everyday life and stirred scientists to think that if bacteria could make the wine "sick",the perhaps they could cause human illness.
Pasteur had to disprove spontaneous generation to sustain his theory, and he therefore devised a series of swan-necked flasks filled with broth. He left the flasks of broth open to the air, but the flasks had a curve in the neck so that microorganisms would fail into the neck, not the broth. The flasks did not become contaminated (as he predicted they would not), and Pasteur's experiments put to rest the notion of spontaneous generation. His work also encouraged the belief that microorganisms were in the air and could cause disease. Pasteur postulated the germ theory of disease, which states that microorganisms are the causes of infectious disease.
Pasteur's attempts to prove the germ theory were unsuccessful. However, the German scientist Robert Koch provided the proof by cultivating anthrax bacteria apart from any other type of organism. He then injected pure cultures of the bacilli invariably caused anthrax. The procedures used by Koch came to be known as Koch's postulates. They provided a set of principles whereby other microorganisms could be related to other diseases.
Anton van Leeuwenhoek
Robert Hooke
John Needham
Lazzaro Spallanzani
Louis Pasteur
Robert Koch
