Biological Diversity 2
the Eubacteria) and blue-green bacteria (the blue-green algae when I was a . Endospores allow bacteria that produce them to survive in the harshest of environments. . Many plants have a symbiotic relationship with bacteria growing in their replication of bacteria, and are produced by microorganisms such as fungi. Some are mutualists (live in a symbiotic relationship where both organisms but rather consist of a fungus and an algae living in mutualistic symbiosis. The spores of fungi are distinct from bacterial endospores, both in structure and function. Each fungus may produce a great number of spores, while a bacterial cell can. endospore, a small, rounded, thick-walled, resting cell that forms inside a symbiosis, a close relationship between two organisms of different species that reproductive structure of a fungus that contains many hyphae and produces spores lichen, a fungus and either algae or autotrophic bacteria that live together in a.
Cell to cell communication is possible through pits in the secondary cell wall that allow plasmodesmata to connect cells through the secondary cell walls. Fungal cell walls[ edit ] Chemical structure of a unit from a chitin polymer chain. There are several groups of organisms that have been called "fungi".
Some of these groups Oomycete and Myxogastria have been transferred out of the Kingdom Fungi, in part because of fundamental biochemical differences in the composition of the cell wall. Most true fungi have a cell wall consisting largely of chitin and other polysaccharides. The fungal cell wall is a matrix of three main components: Both chitin and chitosan are synthesized and extruded at the plasma membrane. Most of the structural proteins found in the cell wall are glycosylated and contain mannosethus these proteins are called mannoproteins or mannans.
The inclusion of additional polysaccharides in algal cells walls is used as a feature for algal taxonomy. They form microfibrils in the cell walls of a number of marine green algae including those from the generaCodiumDasycladusand Acetabularia as well as in the walls of some red algaelike Porphyra and Bangia. It is a common polysaccharide in the cell walls of brown algae. They occur in the cell walls of most algae; those common in red algae include agarosecarrageenanporphyranfurcelleran and funoran.
Other compounds that may accumulate in algal cell walls include sporopollenin and calcium ions. The group of algae known as the diatoms synthesize their cell walls also known as frustules or valves from silicic acid.
Until recently they were widely believed to be fungi, but structural and molecular evidence  has led to their reclassification as heterokontsrelated to autotrophic brown algae and diatoms. Unlike fungi, oomycetes typically possess cell walls of cellulose and glucans rather than chitin, although some genera such as Achlya and Saprolegnia do have chitin in their walls.
Slime molds[ edit ] The dictyostelids are another group formerly classified among the fungi. They are slime molds that feed as unicellular amoebaebut aggregate into a reproductive stalk and sporangium under certain conditions. Cells of the reproductive stalk, as well as the spores formed at the apex, possess a cellulose wall. The cell envelope comprises a plasma membraneseen here in light brown, and a thick peptidoglycan -containing cell wall the purple layer.
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No outer lipid membrane is present, as would be the case in gram-negative bacteria. The red layer, known as the capsuleis distinct from the cell envelope. Cell envelope and Bacterial cell structure Around the outside of the cell membrane is the bacterial cell wall. Bacterial cell walls are made of peptidoglycan also called mureinwhich is made from polysaccharide chains cross-linked by unusual peptides containing D- amino acids.
The cell wall is essential to the survival of many bacteria, although L-form bacteria can be produced in the laboratory that lack a cell wall.
There are broadly speaking two different types of cell wall in bacteria, called gram-positive and gram-negative. The names originate from the reaction of cells to the Gram staina test long-employed for the classification of bacterial species. Like all living organismsbacteria contain ribosomes for the production of proteins, but the structure of the bacterial ribosome is different from that of eukaryotes and Archaea.
Cell envelope Around the outside of the cell membrane is the cell wall. Bacterial cell walls are made of peptidoglycan also called mureinwhich is made from polysaccharide chains cross-linked by peptides containing D- amino acids. The cell wall is essential to the survival of many bacteria, and the antibiotic penicillin is able to kill bacteria by inhibiting a step in the synthesis of peptidoglycan.
The names originate from the reaction of cells to the Gram staina long-standing test for the classification of bacterial species. In contrast, gram-negative bacteria have a relatively thin cell wall consisting of a few layers of peptidoglycan surrounded by a second lipid membrane containing lipopolysaccharides and lipoproteins.
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This includes clinically important bacteria such as Mycobacteria which have a thick peptidoglycan cell wall like a gram-positive bacterium, but also a second outer layer of lipids. S-layers have diverse but mostly poorly understood functions, but are known to act as virulence factors in Campylobacter and contain surface enzymes in Bacillus stearothermophilus. Flagella are driven by the energy released by the transfer of ions down an electrochemical gradient across the cell membrane.
They are distributed over the surface of the cell, and resemble fine hairs when seen under the electron microscope. Ribosomes are the structures in cells where proteins are assembled. Bacterial ribosomes have different sized ribosomal subunits than do eukaryotes. Transmission electron micrograph of several bacterial flagella.
These shaps are shown in Figures 7 and 8. Unicellular, they often stick together forming clumps or filaments. Examples of rod-shaped bacteria. Rod-Shaped Bacterium, hemorrhagic E. H7 division SEM x22, This image is copyright Dennis Kunkel at www. Scanning electron m icrographs illustrating external features of the rod-shaped bacterium E. The middle image above is from: The lower image above is from: Spherical cocoid and spiral bacteria.
Left, a cross-section of a cell illustrating the location of a flagella inside the cell; Center, Borrelia burgdorferi, the organism that causes Lyme disease; and Right, Treponema pallidum, the spirochete that causes the venereal disease syphilis. The image above is from http: Shapes and grouping forms of various bacteria. Bacterial Reproduction Back to Top Prokaryotes are much simpler in their organization than are eukaryotes.
There are a great many more organelles in eukaryotes, as well as more chromosomes to be moved around during cell division. The typical method of prokaryote cell division is binary fissionshown in the animated GIF below as well as in Figure The prokaryotic chromosome is a single DNA molecule that first replicates, then attaches each copy to a different part of the cell membrane.
When the cell begins to pull apart, the two chromosomes thus are separated. Following cell splitting cytokinesisthere are now two cells of identical genetic composition except for the rare chance of a spontaneous mutation. Animated GIF of binary fission. One consequence of this asexual method of reproduction is that all bacterial cells in a colony are genetically the same. When treating a bacterial disease, a drug that kills one bacteria of a specific type will normally kill all other members of that clone colony it comes in contact with.
Evolution requires genetic variation on which to operate. How then can bacteria increase their genetic variation if their typical mode of reproduction produces clones? Bacteria can accomplish genetic recombination in three ways. Conjugation, shown in Figures 11 and 12, is the process where one bacterium passes DNA to another through a tube the sex pilus that temporarily joins the two conjugating cells. Conjugation occurs only between bacteria in same or closely related species.
Transformation involves a bacterium taking up free pieces of DNA secreted by live bacteria or released by dead bacteria. Recall that Griffith's experiment demonstrated this process. The third process, transduction, happens when bacteriophage transfer portions of bacterial DNA from one cell to another.
Certain types of bacteria can "donate" a piece of the their DNA to a recipient cell. The recombination is the bacterial equivalent of sexual reproduction in eukaryotes. Note that the entire DNA is not usually transferred, only a small piece. Top image is from: Diagram of bacterial conjugation. Images from Purves et al. Plasmids sometimes carry genes for resistance to antibiotics.
Since they are also DNA, plasmids can be transferred between bacteria by any of the three processes mentioned above. Since genetic recombination does not routinely happen as it does in sexually reproducing eukaryotesmutation is the most important source of genetic variation for evolutionary change.
Normally bacteria have short generation times, mutations are generated and distributed throughout bacterial populations more quickly than in eukaryotes.
Prokaryotes have only a single chromosome, which makes them haploid. Consequently, mutations are not hidden by a dominant allele, and will be expressed and evaluated by natural selection more rapidly than in diploid eukaryotes.
Endospores are a method of survival, not one of reproduction. The formation of an endospore is shown in Figure Certain bacteria will form a spore inside their cell membrane an endospore that allows them to wait out deteriorating environmental conditions.
A small portion of cytoplasm and a chromosome copy are surrounded by three heavy, protective spore coats.
Difference between Algae and Fungi (Table) | easybiologyclass
The part of the bacterial cell outside the endospore deteriorates and the endospore is released. Endospores allow bacteria that produce them to survive in the harshest of environments. When conditions once again become suitable, the endospore absorbs water and grows out of its spore coat. Certain disease causing bacteria such as Bacillus anthracis, the cause of the disease anthrax can be virulent capable of causing an infection for up to years after forming their endospore! Because of this, as well as other factors, the anthrax bacterium has been considered as a possible biological weapon.
Following the September 11, terrorist attacks, several people died from anthrax exposure, and one postal facility was closed as was the U. Senate building for several weeks.
As of Marchno connection between these events has been definitely established. Electron micrographs illustrating formation of an endospore.
Note, the sequence illustrated here goes from left to right. The above image is from: Classification of Bacteria Back to Top Bacteria are classified on the basis of their method of energy acquisition. Traditional classifications include chemosynthetic, photosynthetic, and heterotrophic groups. Molecular and cladistic studies are reshaping these traditional groups.
In the absence of a consensus the traditional groups are employed here.
Bacteria - Wikipedia
Chemosynthetic Bacteria Chemosynthetic bacteria are autotrophicand obtain energy from the oxidation of inorganic compounds such as ammonia, nitrite to nitrateor sulfur to sulfate. Photosynthetic Bacteria Photosynthetic bacteria carry out conversion of sunlight energy into carbohydrate energy. Cyanobacteria, an example of which is shown in Figure 13, are the major group of photosynthetic bacteria. Some early cyanobacteria may have formed the oxygen released into the early atmosphere, transforming our planet from one with an oxygen-free atmosphere, to the modern one that has a significant amount of oxygen present.
In addition to chlorophyll acyanobacteria also have the blue pigment phycocyanin and the red pigment phycoerythrin. Filamentous cyanobacterium, Anabaena sp.
Eukaryotic autotrophs all have chloroplasts in which the photosynthetic process occurs. The typical chloroplast organization has thylakoids surrounded by a fluid-like stroma. The chloroplast is a membrane bound organelle. Prokaryotes by definition lack such structures. How can bacteria carry out photosynthesis? The answer is shown in Figure By infolding their cell membrane, prokaryotic autotrophs form thylakoids, in effect turning the bacterium into a single chloroplast.
Figure 14 Prochloron, a photosynthetic bacterium that illustrates that even though they lack chloroplasts, photosynthetic bacteria have infoldings of the cell membrane that form thylakoids inside the cell's cytoplasm.
TEM, magnification not known. More primitive photosynthesizing bacteria e. Heterotrophic Bacteria Members of this large and diverse group must derive their energy from another organism by feeding. Saprophytes feed on dead or decaying material and are important nutrient recyclers. Symbiotic bacteria live within a host multicellular organism and contribute to the health of the host. Examples include cows and other grazing animals: Normally cellulose is nondigestible.