First and foremost, fungi are interesting in that they can be both unicellular and multicellular. Most fungi, including molds and mushrooms are multicellular, but yeasts happen to be unicellular, possibly having evolved from multicellular ancestors. Fungi are known as “saprophyte heterotrophs,” meaning that the acquire and process carbon from an outside, organic source, specifically dead or decaying matter. Fungi are distinct in that they can be unicellular, multicellular, or dimorphic (unicellular or multicellular depending upon the conditions). Key structural components of fungi include:
○ Mycelium – Milky mass of branching, threadlike hyphae, often underground.
○ Hyphae – A long, branching, filamentous structure of a fungus that is the main mode of vegetative growth
○ Glucan – Any polymer of glucose
○ Chitin – complex polysaccharide that can also be found in the exoskeletons of arthropods; thought to be responsible for some forms of athsma in humans
○ Thallus – Vegetative body of a fungus
○ Pileus – The “cap” of a fungus most associated with mushrooms
Mechanisms of pathogenesis (how does it cause disease)
The general way that fungi cause disease in humans, is when those fungi become parasitic to the human, and sustaining infection. Interestingly, fungi rarely cause disease in healthy, immuno-competent hosts. It appears that disease results when fungi accidentally penetrate host barriers or when immunologic defects or other debilitating conditions exist that favor fungal entry and growth. Host barriers include previously uncompromised bodily systems, etc. Multiplication within the host is facilitated by virulence mechanisms (ability to grow at up to 37 degree C temperatures, capsule shape) and morphological forms (yeast, sclerotic bodes, spherules). Resistance to fungi are largely based on an innate ability to ward fungi off due to cutaneous and mucosal physical barriers. The fungi cause internal infection, which often result in aspergillosis most commonly affects the lungs, but sometimes infects other organs, cryptococcus’s which is uncommon, but can cause meningitis, and histoplasmosis
Treatment options and how they relate to the biology of the organism
The most common infections come from the fungal group tinea to which ringworm (tinea corporis), ringworm of the scalp (tinea capitis), athlete’s foot (tinea pedis) all belong. Many of the fungi are treated by damaging the cell wall of the fungus, which causes the fungal cell to die. The cell wall, which is integral to the survival of the fungus. Because people generally have a natural resistance to fungi, people are usually only given anti-fungal medication if they are very ill or have a persistent autoimmune deffiviency.
Diseases caused by fungi include:
Key structural components/biology of the organism – Chris
Mechanisms of pathogenesis (how does it cause disease) – Shea
While each protists method of pathogenesis is slightly varied, they work in generally in one of two main ways: either using the host for nutrients or attacking the host directly. Giardia protozoa are examples of the first kind of protist. They enter the host through tainted food or drink, usually that has been in contact with fecal matter. It then implants itself in the lining of the stomach and starts syphoning of resources. This can lead to minor irritation, along with diarrhea, which in turn spread the disease even more.
Malaria acts quite differently. It enter the blood stream through mosquito bites, and finds it way to the liver where it begins multiplying. After a few weeks, the protist bursts and starts affecting red blood cells. When the cells start to die off, the body is unable to oxygenate its cells. This slowly leads to the death of the cells and eventually if untreated the host.
Treatment options and how they relate to the biology of the organism — David
Protists can be hard to treat because as eukaryotic cells they share many common pathways and proteins with human cells. As a result, drugs that target protists are not as easy to develop as antibiotics. A variety of drugs are used against protists, including some in which the mechanism by which it acts is not fully understood. Some drugs, such as Quinine, are alkaloids that lead to the protists having too many cytotoxins inside them. Other drugs target specific proteins that are used commonly by protists. One of the most commonly-used drugs to fight African Sleeping Sickness, Pentamidine, is theorized to inhibit cell functions related to nucleic acids.
The wide genetic diversity of protists and a lack of knowledge and funding about treatment has resulted in many different drugs becoming available to fight protists. There is no single drug that fights all protists and some protists are developing resistance to the drugs that are widely-used to fight them.
Examples of diseases caused by this organism – David
The two most common diseases caused by protists are Malaria, caused by protists of the genus Plasmodium, and African Sleeping Sickness, caused by the protists Trypanosoma brucei gambiense or Trypanosoma brucei rhodesiense.
Infecting and affecting approximately two billion people worldwide per year, helminths are important pathogens on the global scale. Commonly known as parasitic worms, the term “helminth” covers all worms — both parasitic and free-living organisms that often use living hosts as sources for nourishment and protection.
Biologically, helminths are both eukaryotic and multicellular organisms, which are usually large enough by their adult stage to be seen by the human eye. All helminths are symmetrical along a line running from head to tail, and either have tube-like or flattened body structures. While helminth is a group covering many different species, the classification of these worms can be broken down further into three main phyla:
Although helminths can come in different structures and species, they go about infecting humans and animals in fairly similar ways. Helminths make their way into the human body through one of four main ways: fecal-oral transmission (eggs or larvae passed in the faeces of one host and ingested with food/water by another); transdermal transmission (larvae in the soil actively penetrate the skin through contact and migrate through the tissues to the gut where adults develop and produce eggs); vector-borne transmission (larvae are taken up by another animal, such as a fly, and injected into new human hosts); and predator-prey transmission (larvae within animals are then eaten by predators, within which adult worms can develop and produce eggs).
Once helminths have successfully entered the body, they can impair the nutritional status of the host in a variety of ways, namely:
However, these symptoms will mainly occur in humans carrying a large quantity of helminth larvae, and most people infected with smaller quantities will never experience any of these effects.
The main effects of any helminth infection will only manifest as the worm makes its way out of the host in order to continue living and breeding. The most visually jarring of these exits is made by the Guinea Worm (Dracunculus medinensis), which burrows out of the skin in a painful blister, before releasing its eggs in the body of water the host will inevitably put the blister in due to the burning sensation. The more common method of exiting the body is through feces or urine, as the Trematode Schistosoma mansoni does (see this figure).
As parasitic organisms, helminths are often not given the attention they deserve. Unlike many other infectious organisms, there are actually many ways to prevent and treat helminths. The first step to prevent any helminth-induced infection is to follow the directions hidden in the acronym “W.A.S.H.” This stands for water supply, sanitation and hygiene. By defecating and handling waste far from the water supplies, people can better their chance that water supplies stay free of helminth contamination from humans. Next, people can wear shoes and garments in areas meant for waste to avoid infection by burrowing through skin, as helminthes frequently do. By preparing food in clean and sanitized areas, there is a much smaller chance that helminth eggs are ingested.
In terms of treatment options, there seem to be various, but similar options. Antiparasitic drugs are regarded as the best and most effective option of treatment. Too frequently do people try and let the parasite make its way out of the body without physically treating themselves. Antiparasitic drugs have different ways of killing the Helminths and most drugs send the invaders into paralysis. The way that drugs kill the helminths is usually by affecting the nervous system of the worms, and altering the ion-channels on, and inside the parasites membrane. Drugs like Ivermectin work by binding to glutamate-gated chloride ion channels in the helminths nerve and muscle cells causing paralysis of peripheral motor function and death of the worm. It seems that most antiparasitic drugs work this way. Whereas Praziquantel is an antiparasitic which affects the helminths ability to maintain sufficient calcium levels ultimately killing the helminth. An outlier in the medicines is Albendazole, which causes degeneration of cytoplasmic microtubules in intestinal helminths. Most of the drugs work by limiting the helminths ability to live sufficiently, in order to keep the drugs safe enough for human use, while effectively killing off parasites like helminths.
Diseases caused by helminth species include:
Structure of a Virus
A cluster of viral DNA encased in a capsid, a protein coat sometimes encased in a membrane: casings to protect the viral DNA. The virus also has a “body” that includes a neck, collar, sheath, and tail fibers, all made of structure proteins. Here is a diagram of the structure.
Viral method of infection
If the virus has a membrane, the membrane merges with that of the host cell. The cell’s viral DNA then enters the cell and begins taking over the cell’s replication organisms. Most viruses uses the reproduction system of the host cell to replicate its own DNA. The copied viral DNA then exits the cell and moves to infect other host cells. Symptoms come from immune system reactions to this viral takeover. For example, fever as a result of viruses such as the common cold is a precautionary measure to speed up immune reactions and raise the temperature above ideal conditions for virus. Infected cells release cytokines, which are signal enzymes, to attract cells of the immune system such as macrophages to begin to attempt killing off viruses, and to warn surrounding cells of an impending virus to get them to stop replicating. This is how symptoms are felt: excessive mucous, coughing, welts and other marks on this skin (more serious). It is easy for the virus to spread quickly because of its ability to mass produce itself within a cell. They are easier to vaccinate as unless there is any mutation, a vaccine can be developed to give the body immunization to the given virus’ exact DNA/RNA composition. Here is a diagram of the process of viral DNA entering, replicating, and exiting a host cell.
To prevent future infection a vaccine can be given in the form of an injection. The injection is a weakened or dead strand of the virus, but invokes the same immune response. There is not much you can do once you have already been infected by a virus. Antibiotics to not work as they are primarily for bacteria living around and on cells. Viruses are protected because they reside in the nucleus of cells.
DNA (double helix) vs. RNA (single helix, “retroviruses”) viruses
DNA viruses take over the host cell’s replication organelles, and transcribe themselves into RNA. The RNA becomes a means for mass production of new viral DNA. From there, new viruses exit the cell and infect surrounding cells. DNA viruses include Papillomavirus (HPV), Ebola, and the Common Cold. RNA viruses enter the cell and undergo reverse transcription. This means that the converts to DNA using its own enzyme. This enzyme is not particularly accurate and can cause mutation. The virus then spreads itself in the same way as DNA viruses once it has replicated within a host cell. The most notorious retrovirus is HIV.
1. Key structural components/biology of the organism
Bacteria are among the most common kinds of pathogens. They have a cell wall which is frequently marked with biological tags specific to the individual organism. Thus many treatments for bacterial infections attempt to target their cell wall to try and puncture it, causing the bacterium to lyse and be destroyed. Bacterium are prokaryotic single celled organisms. This means that they have no nucleus and no organelles. They collect nutrients from their environments and propel themselves via pili or flagellum.
2. Mechanisms of pathogenesis (how does it cause disease)
Bacteria can enter the body in numerous ways–mouth, skin, nose, etc. If they multiply enough, they cause an infection. These infections are caused by microbes themselves, or by poisons called toxins that they produce. The two main types of toxins utilized by bacteria are endotoxins and exotoxins. Endotoxins are the result of toxins found within the bacterial envelope or cell wall. When the bacteria is killed, this toxin is released by the decomposing cell into the environment. Exotoxins are released by bacteria as a byproduct of their normal metabolism, either being released as a byproduct of their biological processes or as a deliberate action to harm the host.
3. Treatment options and how they relate to the biology of the organism
When someone has a bacterial infection, antibiotics are likely the most effective treatment option. An antibiotic is a medicine that inhibits the growth of, or destroys microorganisms. The first antibiotic, penicillin, was discovered by Alexander Fleming. Penicillin revolutionized doctor’s ability to combat bacterial illness. There are multiple types of antibiotics based on the ways that they disrupt bacteria. A beta-lactam antibiotic kills bacteria that are surrounded by a cell wall. The macrolide group of antibiotics impacts ribosomes and alters protein production. Quinolones are antibiotics that cause DNA strands to break and prevent the breaks from being repaired.
4. Examples of diseases caused by this organism
Tuberculosis is an infection of the lungs which can cause symptoms similar to the flu at first before debilitating or killing the host. TB is one of the rare bacterial infections which will enter the body’s own cells and use them as a host. The Bubonic plague, or Black Death, is transmitted by the bite of an infected flea. The disease can be fatal, first disfiguring its victims with grotesque bubos, pus filled lumps over the body’s lymph nodes. Cholera is diarrheal disease, causing intense dehydration and even death.