Fungi

Fungal Structures

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:

  • Candida
  • Athlete’s Foot
  • Fungal Meningitis

Prions

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How Prions Spread

  1. Prions are proteins that folded improperly, and are characterized as pathogens because when they come into contact with normal proteins, they cause the normal protein to take the malformed shape of the prion, thereby spreading itself.
  2. Prions can appear through various ways, but the most common two are genetic disorders and consuming prions from something else that had them. The problem with the unchecked spread of out-of-shape proteins is that they eventually form into plaques and fibers that shouldn’t be there, as well as losing the functionality of the original protein. This is mostly a problem in the nervous system, the affected area of most prion diseases.
  3. Prion diseases are rough. All of them inevitably lead to death, and there is no cure or effective treatment for any of them yet. Currently scientists are working to find small molecule medicines that can interact with the prions, but we are a long way from seeing any effective medicine to combat prion diseases. Instead most treatment of prion diseases focuses on easing the pain and suffering of the patient until their death.
  4. There are only a few prion diseases in the world today, and they affect only a few thousand people every year, but there are some famous examples of prion diseases.
    1. The first is Mad Cow Disease(also known as Bovine Spongiform Encephalopathy), which spreads from cow to cow when they eat the meat of their brethren. It degrades the nervous system of the infected cows until they die or are slaughtered prematurely, making them seem crazy due to their erratic behavior. If a human eats the meat of an infected cow, the prions can spread to them too and cause Creutzfeldt–Jakob disease.
    2. Another famous and bizarre prion disease is Kuru. Native to the Fore Tribe in Papua New Guinea that eat their dead as a funereal ritual, Kuru is the Fore word for “to shake”, for the tremors that the disease causes. The disease, like most transmissible prion diseases, is caused by the consumption of someone who already had the disease. Fortunately, there are normally fewer than one case a year now.
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Structure of a Prion

Works Cited:

https://www.ncbi.nlm.nih.gov/pubmed/18233951

http://www.hopkinsmedicine.org/healthlibrary/conditions/nervous_system_disorders/prion_diseases_134,56/

http://www.prionalliance.org/2014/02/04/what-are-the-potential-treatments-for-prion-disease/

http://www.fda.gov/AnimalVeterinary/ResourcesforYou/AnimalHealthLiteracy/ucm136222.htm

http://anthropology.ua.edu/bindon/ant570/Papers/McGrath/McGrath.htm

Protists Overview

Key structural components/biology of the organism – Chris

  • Protist are eukaryotic cells. This means they have a nucleus and other membrane-bound organelles. Protist cells are very unique because all are distinct and different from each other. Protist also have their own kingdom which is called the Kingdom Protist.
  • Most Protist cells are unicellular which means that they are one celled eukaryotes.  Very few Protist cells are multicellular which means that they have many cells within. An example of a multicellular Protist cell is Kelp. Kelp can grow up to 100 meters in an aquatic environment. Multicellular and Unicellular do not show cellular specialization or differentiation in the tissues of the cell. Most Protist cells appear to look the same and function the same but are all unique and different than one another. Protist are able to be parasites and prefer either aquatic or moist environments. Most Protist also have mitochondria in their structure.
  • Protist can be classified in 3 different ways. Protist can be classified as animals cells. This means that they are able to move. Protist can be classified as plant cells. This means that the plant has autotrophs that photosynthesize. Protist can be classified as Fungi cells. Fungi are heterotrophs which means it has cells with cells walls that are able to reproduce. Protist are eukaryotic but are not able to be classified as an animal, plant, or fungi cells. Protist has a very simple cell structure but use the classification of plant, animal, and fungi  to help show the characteristics of the cell.
  • There are many different types of Protist but I will highlight the most common Protist. Protist are able to move three different ways. Protist are able to use there cilia. The cilia use microscopic hair called cilia to move. The tiny hairs flap together to help move. Protist are able to use there flagella which is a long tail that moves back and forth helping to propel the cell forward. Protist are able to use there Pseudopodia which extends part of its cell body to scoot or ooze along.
  • The Protist are able to eat by gathering energy in different ways. They eat food and digest it internally or digest the food outside of their body by secreting enzymes. They are also are able to eat pre digested food. They are also able to get energy from photosynthesis which absorbs sunlight and uses the absorbed energy to make glucose.

 

 

 

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.

Helminths

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.

howtheimmune

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:

  1. Nematodes

    Most commonly known as roundworms, the phylum Nematoda contain the tube-like helminths, clearly distinguishable from the other phyla on account of their cylindrical bodies. The main feature interrupting a nematode’s outer skin is its anterior mouth, its main source of nutrient intake. The mouth feeds into a fluid-filled cavity which then acts as a skeleton, providing rigidity for the organism when needed. On a more specific level, the orders of nematodes that infect humans and domestic animals include Trichocephalida, Oxyurida, Ascaridida, Strongylida, Rhabditida, Camallanida, and Spirurida. Nematodes move by using longitudinal muscles to thrash sideways. Although nematode eggs do not have a defined gender, adult organisms form separate sexes with well-developed reproductive systems.

  2. Cestodes

    Also referred to as tapeworms, the phylum Cestoda contain some of the flatter helminths, and are generally longer and ribbon-shaped. Cestodes are broken into numerous segments, and have a scolex (an organ on the head used to attach to the host). Cestodes have evolved to become flat enough to perfuse to internal tissues — such as the lining of a digestive tract — and as a result do not have a stomach or any internal cavities. Because cestodes will attach themselves to the lining of a tissue, they do not have any demand for complex muscle structures and absorb nutrients in the most efficient manner: through their skin. All cestodes are hermaphroditic, with each segment housing both male and female reproductive organs.

  3. Trematodes

    Commonly called flukes, the phylum Trematoda contain the smallest of the helminths: these helminths are both flat and leaf-like. Trematodes closely resemble cestodes, and also lack any internal cavities, as well as (most) Trematodes being hermaphroditic, with only a few exceptions. Trematode motion is the result of a complex muscle systems, which help the worms glide over objects easily.

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:

  • A loss of iron and protein caused by the worms feeding on host tissues and blood.
  • Malabsorption of nutrients.
  • Vitamin A deficiency, caused by nematodes (roundworms) competing for vitamin A in the intestine.
  • Loss of appetite and, therefore, a reduction of nutritional intake and physical fitness.

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:

  • Hookworm disease: Caused by the nematodes Ancylostoma duodenale or Necator americanus. When infected, hookworm disease can result in anemia and malnutrition.
  • Dracunculiasis or Guinea Worm disease: Caused by the nematode Dracunculus medinensis, this disease is transmitted through contaminated water. The worm burrows out from the skin causing severe inflammatory reactions and discomfort.
  • Loiasis: Caused by the nematode Loa loa, Loiasis is transmitted through Deer fly or Mango fly bites (where the flies contain Loa loa larvae). Once inside of a human host, adult worms move through tissue towards the inner eye. Loiasis causes red, itchy swellings in the skin referred to as Calabar swellings.
  • Cysticercosis:Caused by the cestode Taenia solium. Symptoms only become evident when enough worms have taken refuge in their host — a process which often takes years — eventually resulting in painless bumps on the skin and muscles, or neurological problems.
  • Echinococcosis: Caused by the cestode genus Echinococcus, Echinococcosis usually targets the liver first, before moving to the lungs and brain. Early stages can be felt by abdominal pain and jaundice, while the disease’s spread to the lungs is accompanied by breathlessness and coughing.

Viruses

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.

Treatment method

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.

Bacteria

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.

 

 

 

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