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Do all fungi dislike acidic environments?

Do all fungi dislike acidic environments?


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I know that some fungi prefer mildly alkaline environments and dislike acidic environments. Is that true of all fungi, or do some fungi prefer acidic environments? If so, are such acidic fungi rare exceptions or is it common for there to be acid-loving fungi?


Fungi that grow in acidic media are well known, here just one reference: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC518635/pdf/jbacter00651-0183.pdf

About their spread, they are less common in mild environments (like you hands, or your garden soil) but of course in acidic environments, they will be predominant.


Endomycorrhizal fungi

Endomycorrhizal fungi (more commonly referred to as endomycorrhizae) is one of the major types of known mycorrhizae which differs from the another type of mycorrhizae, ectomycorrhizae, in structure. Unlike ectomycorrhizae which form a system of hyphae that grow around the cells of the root, the hyphae of the endomycorrhizae not only grow inside the root of the plant but penetrate the root cell walls and become enclosed in the cell membrane as well (1). This makes for a more invasive symbiotic relationship between the fungi and the plant. The penetrating hyphae create a greater contact surface area between the hyphae of the fungi and the plant. This heightened contact facilitates a greater transfer of nutrients between the two. Endomycorrhizae have further been classified into five major groups: arbuscular, ericoid, arbutoid, monotropoid, and orchid mycorrhizae (2).


YEASTS

Yeasts are unicellular, oval or spherical fungi which increase in number asexually by a process termed budding (see Fig. 1). A bud forms on the outer surface of a parent cell, the nucleus divides with one nucleus entering the forming bud, and cell wall material is laid down between the parent cell and the bud. Usually the bud breaks away to become a new daughter cell but sometimes, as in the case of the yeast Candida, the buds remain attached forming fragile branching filaments called hyphae (see Fig. 10). Because of their unicellular and microscopic nature, yeast colonies appear similar to bacterial colonies on solid media. It should be noted that certain dimorphic fungi (see Lab 10) are able to grow as a yeast or as a mold, depending on growth conditions.

  • Scanning electron micrograph of Saccharomyces courtesy of Dennis Kunkel's Microscopy .
  • Transmission electron micrograph of Candida albicans(see Fig. 3).
  • Movie of Saccharomyces cerevisiae reproducing by budding. Movie of Growth and Division of Budding Yeast (Saccharomyces cerevisiae) . © Phillip Meaden, author. Licensed for use, ASM MicrobeLibrary.

Yeasts are facultative anaerobes and can therefore obtain energy by both aerobic respiration and anaerobic fermentation. The vast majority of yeasts are nonpathogenic and some are of great value in industrial fermentations. For example, Saccharomyces species are used for both baking and brewing.

The yeast Candida is normal flora of the gastrointestinal tract and is also frequently found on the skin and on the mucous membranes of the mouth and vagina. Candida is normally held in check in the body by:

1. normal immune defenses, and

However, Candida may become an opportunistic pathogen and overgrow an area of colonization if the host becomes immunosuppressed or is given broad-spectrum antibiotics that destroy the normal bacterial flora. (Since Candida is eukaryotic, antibiotics used against prokaryotic bacteria do not affect it.)

Any infection caused by the yeast Candida is termed candidiasis. The most common forms of candidiases are oral mucocutaneous candidiasis (thrush see Fig. 7A), vaginitis (see Fig. 7B), balantitis (infection of the penis), onychomycosis (infection of the nails), and dermatitis (diaper rash and other infections of moist skin). In addition, Candida can cause urinary tract infections. However, antibiotic therapy, cytotoxic and immunosuppressive drugs, and immunosuppressive diseases such as diabetes, leukemias, and AIDS can enable Candida to cause severe opportunistic systemic infections involving the skin, lungs, heart, and other organs. In fact, Candida now accounts for 10% of the cases of septicemia. Candidiasis of the esophagus, trachea, bronchi, or lungs, in conjunction with a positive HIV antibody test, is one of the indicator diseases for AIDS.

The most common Candida species causing human infections is C. albicans, causing 50-60% of all Candida infections. Candida glabrata is second, causing 15-20% of Candida infections Candida parapsilosis is third, responsible for 10-20%.

Candida is said to be dimorphic, that is it has two different growth forms. It can grow as an oval, budding yeast, but under certain culture conditions, the budding yeast may elongate and remain attached producing filament-like structures called pseudohyphae. C. albicans may also produce true hyphae similar to molds. In this case long, branching filaments lacking complete septa form. The pseudohyphae and hyphae help the yeast to invade deeper tissues after it colonizes the epithelium. Asexual spores called blastoconidia (blastospores) develop in clusters along the hyphae, often at the points of branching. Under certain growth conditions, thick-walled survival spores called chlamydoconidia (chlamydospores) may also form at the tips or as a part of the hyphae (see Fig. 2A and Fig. 2B)

A lesser known but often more serious pathogenic yeast is Cryptococcus neoformans. Like many fungi, this yeast can also reproduce sexually and the name given to the sexual form of the yeast is Filobasidiella neoformans. It appears as an oval yeast 5-6 µm in diameter, forms buds with a thin neck, and is surrounded by a thick capsule. It does not produce pseudohyphae and chlamydospores. The capsule enables the yeast to resist phagocytic engulfment. The yeast is dimorphic. In its sexual form, as well as in its asexual form under certain conditions, it can produce a hyphal form.

Cryptococcus infections are usually mild or subclinical but, when symptomatic, usually begin in the lungs after inhalation of the yeast in dried bird feces. It is typically associated with pigeon and chicken droppings and soil contaminated with these droppings. Cryptococcus, found in soil, actively grows in the bird feces but does not grow in the bird itself. Usually the infection does not proceed beyond this pulmonary stage. However, in an immunosuppressed host it may spread through the blood to the meninges and other body areas, often causing cryptococcal meningoencephalitis. Any disease by this yeast is usually called cryptococcosis.

Dissemination of the pulmonary infection can result in severe and often fatal cryptococcal meningoencephalitis. Cutaneous and visceral infections are also found. Although exposure to the organism is probably common, large outbreaks are rare, indicating that an immunosuppressed host is usually required for the development of severe disease. Extrapulmonary cryptococcosis, in conjunction with a positive HIV antibody test, is another indicator disease for AIDS. People with AIDS-associated cryptococcal infections account for 80%-90% of all patients with cryptococcosis.

Cryptococcus can be identified by preparing an India ink or nigrosin negative stain of suspected sputum or cerebral spinal fluid in which the encapsulated, budding, oval yeast cells (see Fig. 4A) may be seen. It can be isolated on Saboraud Dextrose agar and identified by biochemical testing. Direct and indirect serological tests (discussed in Labs 17 & 18) may also be used in diagnosis.

Pneumocystis jiroveci, (formerly called Pneumocystis carinii), causes an often-lethal disease called Pneumocystis pneumonia (PCP). It is seen almost exclusively in highly immunosuppressed individuals such as those with AIDS, late stage malignancies, or leukemias. PCP and a positive HIV-antibody test is one of the more common indicators of AIDS.

P. jiroveci can be found in 3 distinct morphologic stages:

  • The trophozoite(trophic form), a haploid amoeboid form 1-4 µm in diameter that replicates by mitosis and binary fission. The trophic forms are irregular shaped and often appears in clusters.
  • A precystic form or early cyst. Haploid trophic forms conjugate and produce a diploid precyst form or sporocyte.
  • The precyst form matures into a cyst form, which contains several intracystic bodies or spores are 5-8 µm in diameter. It has been postulated that in formation of the cyst form (late phase cyst), the zygote undergoes meiosis and subsequent mitosis to typically produce eight haploid ascospores (sporozoites) See Fig. 9. As the haploid ascospores are released the cysts often collapse forming crescent-shaped bodies (see Fig. 5). P. jiroveci is usually transmitted by inhalation of the cyst form. Released ascospores then develop into replicating trophic forms that attach to the wall of the alveoli and replicate to fill the alveoli.
    • Proposed life cycle for Pneumocystis jiroveci from dpd.cdc.gov

    In biopsies from lung tissue or in tracheobronchial aspirates, both a trophic form about 1-4 µm in diameter with a distinct nucleus and a cyst form between 5-8 µm in diameter with 6-8 intracystic bodies (ascospores) can be seen.

    When viewing cysts of P. jiroveci in lung tissue after utilizing the Gomori methenamine silver stain method, the walls of the cysts are stained black and often appear crescent shaped or like crushed ping-pong balls. The intracystic bodies are not visible with this stain.


    Mutualistic Relationships

    Symbiosis is the ecological interaction between two organisms that live together. The definition does not describe the quality of the interaction. When both members of the association benefit, the symbiotic relationship is called mutualistic. Fungi form mutualistic associations with many types of organisms, including cyanobacteria, algae, plants, and animals.

    Fungus-Plant Mutualism

    One of the most remarkable associations between fungi and plants is the establishment of mycorrhizae. Mycorrhiza, which comes from the Greek words myco meaning fungus and rhizo meaning root, refers to the association between vascular plant roots and their symbiotic fungi. Somewhere between 80 and 90 percent of all plant species have mycorrhizal partners. In a mycorrhizal association, the fungal mycelia use their extensive network of hyphae and large surface area in contact with the soil to channel water and minerals from the soil into the plant. In exchange, the plant supplies the products of photosynthesis to fuel the metabolism of the fungus.

    There are a number of types of mycorrhizae. Ectomycorrhizae (“outside” mycorrhiza) depend on fungi enveloping the roots in a sheath (called a mantle) and a Hartig net of hyphae that extends into the roots between cells (Figure 5).

    Figure 5. (a) Ectomycorrhiza and (b) arbuscular mycorrhiza have different mechanisms for interacting with the roots of plants. (credit b: MS Turmel, University of Manitoba, Plant Science Department)

    The fungal partner can belong to the Ascomycota, Basidiomycota or Zygomycota. In a second type, the Glomeromycete fungi form vesicular–arbuscular interactions with arbuscular mycorrhiza (sometimes called endomycorrhizae). In these mycorrhiza, the fungi form arbuscules that penetrate root cells and are the site of the metabolic exchanges between the fungus and the host plant (Figure 5 and Figure 6). The arbuscules (from the Latin for little trees) have a shrub-like appearance. Orchids rely on a third type of mycorrhiza. Orchids are epiphytes that form small seeds without much storage to sustain germination and growth. Their seeds will not germinate without a mycorrhizal partner (usually a Basidiomycete). After nutrients in the seed are depleted, fungal symbionts support the growth of the orchid by providing necessary carbohydrates and minerals. Some orchids continue to be mycorrhizal throughout their lifecycle.

    Figure 6. The (a) infection of Pinus radiata (Monterey pine) roots by the hyphae of Amanita muscaria (fly amanita) causes the pine tree to produce many small, branched rootlets. The Amanita hyphae cover these small roots with a white mantle. (b) Spores (round bodies) and hyphae (thread-like structures) are evident in this light micrograph of an arbuscular mycorrhiza between a fungus and the root of a corn plant. (credit a: modification of work by Randy Molina, USDA credit b: modification of work by Sara Wright, USDA-ARS scale-bar data from Matt Russell)

    Practice Question

    If symbiotic fungi are absent from the soil, what impact do you think this would have on plant growth?

    Other examples of fungus–plant mutualism include the endophytes: fungi that live inside tissue without damaging the host plant. Endophytes release toxins that repel herbivores, or confer resistance to environmental stress factors, such as infection by microorganisms, drought, or heavy metals in soil.

    Coevolution of Land Plants and Mycorrhizae

    Mycorrhizae are the mutually beneficial symbiotic association between roots of vascular plants and fungi. A well-accepted theory proposes that fungi were instrumental in the evolution of the root system in plants and contributed to the success of Angiosperms. The bryophytes (mosses and liverworts), which are considered the most primitive plants and the first to survive on dry land, do not have a true root system some have vesicular–arbuscular mycorrhizae and some do not. They depend on a simple rhizoid (an underground organ) and cannot survive in dry areas. True roots appeared in vascular plants. Vascular plants that developed a system of thin extensions from the rhizoids (found in mosses) are thought to have had a selective advantage because they had a greater surface area of contact with the fungal partners than the mosses and liverworts, thus availing themselves of more nutrients in the ground.Fossil records indicate that fungi preceded plants on dry land. The first association between fungi and photosynthetic organisms on land involved moss-like plants and endophytes. These early associations developed before roots appeared in plants. Slowly, the benefits of the endophyte and rhizoid interactions for both partners led to present-day mycorrhizae up to about 90 percent of today’s vascular plants have associations with fungi in their rhizosphere. The fungi involved in mycorrhizae display many characteristics of primitive fungi they produce simple spores, show little diversification, do not have a sexual reproductive cycle, and cannot live outside of a mycorrhizal association. The plants benefited from the association because mycorrhizae allowed them to move into new habitats because of increased uptake of nutrients, and this gave them a selective advantage over plants that did not establish symbiotic relationships.

    Lichens

    Lichens display a range of colors and textures (Figure 7) and can survive in the most unusual and hostile habitats. They cover rocks, gravestones, tree bark, and the ground in the tundra where plant roots cannot penetrate. Lichens can survive extended periods of drought, when they become completely desiccated, and then rapidly become active once water is available again.

    Figure 7. Lichens have many forms. They may be (a) crust-like, (b) hair-like, or (c) leaf-like. (credit a: modification of work by Jo Naylor credit b: modification of work by “djpmapleferryman”/Flickr credit c: modification of work by Cory Zanker)

    Figure 8. This cross-section of a lichen thallus shows the (a) upper cortex of fungal hyphae, which provides protection the (b) algal zone where photosynthesis occurs, the (c) medulla of fungal hyphae, and the (d) lower cortex, which also provides protection and may have (e) rhizines to anchor the thallus to the substrate.

    Lichens are not a single organism, but rather an example of a mutualism, in which a fungus (usually a member of the Ascomycota or Basidiomycota phyla) lives in close contact with a photosynthetic organism (a eukaryotic alga or a prokaryotic cyanobacterium) (Figure 8). Generally, neither the fungus nor the photosynthetic organism can survive alone outside of the symbiotic relationship. The body of a lichen, referred to as a thallus, is formed of hyphae wrapped around the photosynthetic partner. The photosynthetic organism provides carbon and energy in the form of carbohydrates. Some cyanobacteria fix nitrogen from the atmosphere, contributing nitrogenous compounds to the association. In return, the fungus supplies minerals and protection from dryness and excessive light by encasing the algae in its mycelium. The fungus also attaches the symbiotic organism to the substrate.

    The thallus of lichens grows very slowly, expanding its diameter a few millimeters per year. Both the fungus and the alga participate in the formation of dispersal units for reproduction. Lichens produce soredia, clusters of algal cells surrounded by mycelia. Soredia are dispersed by wind and water and form new lichens.

    Lichens are extremely sensitive to air pollution, especially to abnormal levels of nitrogen and sulfur. The U.S. Forest Service and National Park Service can monitor air quality by measuring the relative abundance and health of the lichen population in an area. Lichens fulfill many ecological roles. Caribou and reindeer eat lichens, and they provide cover for small invertebrates that hide in the mycelium. In the production of textiles, weavers used lichens to dye wool for many centuries until the advent of synthetic dyes.

    Fungus-Animal Mutualism

    Figure 9. A leaf cutting ant transports a leaf that will feed a farmed fungus. (credit: Scott Bauer, USDA-ARS)

    Fungi have evolved mutualisms with numerous insects in Phylum Arthropoda: jointed, legged invertebrates. Arthropods depend on the fungus for protection from predators and pathogens, while the fungus obtains nutrients and a way to disseminate spores into new environments. The association between species of Basidiomycota and scale insects is one example. The fungal mycelium covers and protects the insect colonies. The scale insects foster a flow of nutrients from the parasitized plant to the fungus. In a second example, leaf-cutting ants of Central and South America literally farm fungi. They cut disks of leaves from plants and pile them up in gardens (Figure 9). Fungi are cultivated in these disk gardens, digesting the cellulose in the leaves that the ants cannot break down. Once smaller sugar molecules are produced and consumed by the fungi, the fungi in turn become a meal for the ants. The insects also patrol their garden, preying on competing fungi. Both ants and fungi benefit from the association. The fungus receives a steady supply of leaves and freedom from competition, while the ants feed on the fungi they cultivate.


    Factors that Affect Yeast Growth

    Yeast is a unicellular or a single cell organism that belongs to the broader group of organisms known as ‘fungi.’ They sometimes appear as multi cellular structures although these are false or pseudohyphaes in contrast to true hyphaes seen among other fungi.

    Characteristics of yeasts:

    There are about 1500 yeast species identified by scientists although 99% of the same species remains undiscovered. Among the identified species, some require oxygen to perform cellular breathing whereas others can even sustain in environments deprived of oxygen as they have the ability to perform anaerobic cellular respiration. Yeast derives its energy requirements from organic compounds, which are most likely to be sugar based. Due to this phenomenon, these organisms do not depend on sun light for its energy requirements and is often isolated naturally from sugar rich mediums.

    Among many factors that affect the growth of yeast, some are manipulative through various mechanisms. However, not all yeasts thrive on same environmental states and therefore needs individualized attention according to the type of species when cultured in the lab.

    Factors affecting yeast growth:

    Following is a brief description of factors controlling how yeasts grow.

    Yeasts can tolerate extreme temperatures although it may lose its viability with time. Some yeast live in freezing conditions but many will grow in normal environmental temperatures existing in many places. Therefore, refrigeration or deep freezing may not be a full proof method to prevent yeast formation.

    Many species of yeast grow in media with a neutral PH or slightly acidic PH. Thus, yeast extracts or foods derived from yeasts are more likely to be acidic. When it comes to culture medium, scientists use the same characteristic in organic acids for its use as an effective culture medium.

    As described earlier, yeasts require organic compounds such as sugar derivatives to obtain energy and therefore its concentration in the culture medium or in the environment will affect the rate of its growth.

    Certain strains or species of yeasts will grow rapidly whereas some may be relatively slow. However, further research is required to link type of strain and its growth to understand its correlation better.

    As described earlier, although anaerobic respiration is possible, many yeast strains will require oxygen enriched medium for its metabolic functions. Thus, when yeasts grow in a lab, they receive an aerobic environment for effective growth.

    Minerals such as magnesium, potassium and several other trace elements are essential for yeast growth and therefore should encourage growth when provided externally.

    When considering its part as an element in the nucleic acids and phospholipids, provision of phosphorus is important for effective yeast growth.

    It is an essential element of certain amino acids and when added to a culture medium, it will encourage yeast growth.

    Scientists have learn that, yeasts require certain vitamins, purines, pyrimidines, amino acids, fatty acids&hellipetc for catalyzing the biosynthesis although they do not act as energy sources for yeasts. Therefore, such factors are named as &lsquogrowth factors&rsquo and should be available in trace quantities in the culture medium for optimal growth.

    Apart from the above, there can be many other factors contributing to the growth of yeast and require further research to determine how extensively they affect in their growth..


    1.1: Introduction to Microbiology

    Study the material in this section and then write out the answers to these questions. Do not just click on the answers and write them out. This will not test your understanding of this tutorial.

    1. List 5 basic groups of microbes. (ans)
    2. State 3 of the many benefits from microbial activity on this planet. (ans)
    3. State 2 of the harmful effects associated with microbial activities. (ans)
    4. Briefly describe two different beneficial things the human microbiome does for the normal function of our body. (ans)

    Fungal Fermentation for Medicinal Products

    1 INTRODUCTION

    Fungi have played important roles as foods and medicines in both ancient and modern biotechnological processes. Fungi range from microscopic yeasts and molds to macroscopic mushrooms. Their applications include production of antibiotics, alcohols, enzymes, organic acids, and numerous pharmaceuticals. The advent of recombinant DNA technology enables fungi to utilize novel carbon sources and to be hosts for the production of heterogonous proteins. Although several reviews of fungi as microbial cell factories for food use [ 1–3 ] and enzyme production [ 4 , 5 ] have been published recently, reviews of fungi as cell factories for medicinal products are relatively limited and scattered.

    Recently, new drug candidates from fungi have been found with anti-tumor, antihypertensive, immunosuppressant, anti-diarrheal, or anti-mutagenic properties. Increasing scientific evidence from animal tests and clinical studies has supported the idea that some fungi could be used as adjuvant cancer treatments. Thus, fungi play important roles in the booming nutraceutical and functional food markets. Although more scientific evidence is required to substantiate the therapeutical effects of medicinal fungi, possible healing mechanisms and their key compounds have been proposed. This review highlights fungal medicinal products, their therapeutical potential and engineering aspects in manufacturing these products.


    Introduction

    Terrestrial ecosystems are a major source of nitrous oxide (N2O) 1,2 , a so-called greenhouse gas also commonly known as laughing gas. Although it has received much less attention than CO2, the 100 year global warming potential of N2O is 298 times greater than that of CO2 due to the much longer half life of N2O 3 . There is also growing concern over nitrous oxide concentrations because, following the reduction of chlorine- and bromine-containing halocarbons by the Montreal Protocol, N2O has become the main ozone-depleting substance emitted to the stratosphere 4 .

    Nitrous oxide emissions are mostly due to two microbial processes: nitrification and denitrification. Nitrous oxide is a by-product of the first step of nitrification, the oxidation of ammonia to nitrite 5 . In contrast, N2O is either an intermediate or the end product of the denitrification cascade, which consists in the reduction of nitrate or nitrite into nitric oxide, nitrous oxide and dinitrogen 6 . Sixty-two percent of the total global N2O emissions are from natural and agricultural soils (6 and 4.2 Tg N yr −1 , respectively 7 ) and denitrification is traditionally considered as the main source of these emissions 8 .

    It is well known that denitrification is widespread among prokaryotes—indeed, the ability to denitrify has been observed in more than 60 bacterial and archaeal genera 9 . Moreover, eukaryotes such as fungi in soils 10 or foraminifers in aquatic environments 11,12 are also capable of denitrification. Characterization of the fungal denitrification ability in Fusarium oxysporum and Cylindrocarpon tonkinense has shown that this reductive process was performed via a copper-containing nitrite reductase (NirK) and cytochrome P450 nitric oxide reductase 10 . However, no nitrous oxide reductase has been identified in fungi and N2O is the end product of denitrification in the few characterized fungal strains 13,14 . By using fungal or bacterial inhibitors to distinguish the microbial origin of N2O, previous studies have reported that fungi could contribute up to 18% of potential denitrification 15 and be significant N2O producers in some terrestrial systems 16,17 . Despite the importance of fungi in several soil functions, such as organic matter decomposition 18 and primary production through symbiotic or pathogenic relationships with plants 19 , the production of N2O by fungi has only been studied in a limited number of strains 14,20 . To what extent this trait is conserved amongst fungi remains unknown, but understanding the microbial sources of this greenhouse gas will be crucial for selecting mitigation strategies. Here, we screened a collection of 207 fungal strains belonging to 9 classes and 23 orders to determine the prevalence of the N2O-producing capacity among fungi. We further characterized the initial and end-products of denitrification of the N2O production-positive strains in pure culture and determined their N2O isotopic signature. Positive fungal strains were also inoculated into pre-sterilized arable, forest and grassland soils in order to verify their ability to produce this greenhouse gas in soil. Finally, we studied the phylogeny of the nirK gene, which encodes the copper-containing nitrite reductase using newly developed primers and investigated the relationships between the nuclear ribosomal internal transcribed spacer (ITS) region and nirK phylogeny, N2O production rates and N2O isotopic signatures.


    Organisms are now classified into three domains and six kingdoms. The domains include Eukaryota, Eubacteria, and Archaea. Under the archaea domain, there are three main divisions or phyla. They are: Crenarchaeota, Euryarchaeota, and Korarchaeota.

    Crenarchaeota

    Crenarchaeota consist mostly of hyperthermophiles and thermoacidophiles. Hyperthermophilic microorganisms live in extremely hot or cold environments. Thermoacidophiles are microscopic organisms that live in extremely hot and acidic environments. Their habitats have a pH between 5 and 1. You would find these organisms in hydrothermal vents and hot springs.

    Crenarchaeota Species

    Examples of Crenarchaeotans include:

    • Sulfolobus acidocaldarius - found near volcanic environments in hot, acidic springs containing sulfur.
    • Pyrolobus fumarii - live in temperatures between 90 and 113 degrees Celsius.

    Euryarchaeota

    Euryarchaeota organisms consist mostly of extreme halophiles and methanogens. Extreme halophilic organisms live in salty habitats. They need salty environments to survive. You would find these organisms in salt lakes or areas where sea water has evaporated.
    Methanogens require oxygen free (anaerobic) conditions in order to survive. They produce methane gas as a byproduct of metabolism. You would find these organisms in environments such as swamps, wetlands, ice lakes, the guts of animals (cow, deer, humans), and in sewage.

    Euryarchaeota Species

    Examples of Euryarchaeotans include:

    • Halobacterium - include several species of halophilic organisms that are found in salt lakes and high saline ocean environments.
    • Methanococcus - Methanococcus jannaschii was the first genetically sequenced Archaean. This methanogen lives near hydrothermal vents.
    • Methanococcoides burtonii - these psychrophilic (cold-loving) methanogens were discovered in Antarctica and can survive extremely cold temperatures.

    Korarchaeota

    Korarchaeota organisms are thought to be very primitive life forms. Little is currently known about the major characteristics of these organisms. We do know that they are thermophilic and have been found in hot springs and obsidian pools.


    Fungi - good guys or bad guys?

    This is a question that comes up often enough. Some people look on fungi as slimy, yucky, horrible things - with no redeeming features. Others pursue them with great joy - either for digestive delight or because of their inherent beauty. What is the truth? Well, some of them are slimy and yucky. Just look at this species of Hygrocybe, its slimy, gelatinous coat glistening in the camera's flashlight. But imagine a mass of these carpeting the forest floor - surely a delight to the eye.

    Fungi have numerous interactions with other organisms. Parasitic and mycorrhizal lifestyles have already been mentioned. Obviously the parasite is bad for the host while mycorrhizae are beneficial to both plant and fungus. So fungi are inherently neither good nor bad. This page gives just a very brief introduction to the fungal world and elsewhere in this site there's more detail about the roles fungi play. Whether a particular interaction is good or bad will sometimes be a matter of perspective.

    If you're a forester, then a wood-rotting fungus that destroys the heartwood in a tree is going to be a serious pest in your eyes because there's an economic loss. From the tree's point of view, the same fungus may be neither harmful nor beneficial. The heartwood is dead wood, with the living tissue confined to a relatively thin skin under the bark. As long as the fungus is not harming that living skin the tree can go on living quite happily. In fact, there are numerous old, healthy, hollowed-out trees in existence. Moreover, an empty cylinder (such as a hollowed trunk) can resist some stresses better than a solid cylinder (such as a solid trunk). If you're a possum or a parrot, then you'd probably look very favourably on that fungus because it is helping to create potential nesting hollows.

    So here we have three different views on the same fungus.


    Watch the video: Αντιμετωπίστε τους μύκητες των ποδιών με φυσικούς τρόπους. Teta Kampoureli (February 2023).