Arxiu d'etiquetes: mold

Home’s micro-squatters

If you ever thought to be alone in your house, you were wrong. In your home there are thousands and thousands of micro-organisms sprout at ease. They are responsible for odors and pollution from yourhome. Would you like to know more about your tenants?

MICRO-SQUATTERS OF OUR HOUSES

It is stimated that about 90% if our time is spended in closed places, such as office, school or home. These places, as well as the rest of our planet, presents a environmental conditions suitable for proliferation of bacteria, fungi and arthropods. These communities are known as the Home’s Microbiome.

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Photomicrograph of the bristle of a used toothbrush where proliferate a lot of microbial communities (Image: Science photo library)

The relations that we stablish with these communities of microorganisms can condition directly in our health. Can find beneficial microorganisms, indifferent microorganisms (i.e that do not produce any effect) and pathogenic microorganism (as Staphylococcus auereus resistant to antibiotics) or allergens as them mites. These pathogens, in most of cases, just represent a litle percentage and not pose any risk for them home’s occupants.

BACTERIA

Bacterial communities are very abundant in our homes. We can find them in every corner and have a great diversity. For example, in the dust is estimated that there are som 7000 different bacterial species. In the following graphic, can observe the broad diversity of bacterial species that colonizes certain regions of our home, such as the toilet’s lid, kitchen or our own beds.

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Differents bacterial families that we can found arround our home (Image: G.E. Flores)

FUNGI

In normal conditions, a house can present up to 2000 different types from fungi. We can also find them in all home environment such as food, kitchen, walls and even in forgotten places during cleaning as for example the dust accumulated on the door frames. Among them, we can highlight the presence of Aspergillus, Penicillium and Fusarium (common envirnmental fungi). Also proliferate fungi responsible of the wood degradation (as for example Stereum, Tremetes, or Tremellosa) or fungi related with humans, like Candida.

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Wall mold that appear in homes (Image: Mycleaningproduct.com) or fruit mold by Penicillium sp. (image: wisegeek).

MITES

These microorganisms represents to the Arthropods of our homes. Normally they live in dust, on rough surfaces such as fabrics, mattresses and pillowsa where they feed on died human and animals skin. We can find Dermatophagoides pteronyssus and Dermatophagoides farinae species, commonly knwon as dust mites. Even so, and to a lesser extent, we can find also some that another exemplay of Demodex folliculorum. This mite live in the hair follicles of our face and feeds on dead skin. Normally follows from the skin while we are sleeping.

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Dust mite D. pteronyssinus (image: Göran Malmberg) and follicles mite Demodex folliculorum (Image: BBC)

BIOGEOGRAPHY AND  EMISSION SOURCES

The geographical distribution of these microscopic communities and those factors that determine it, are little known. For that reason, along this decade, studies about hom’s microbiome have increased and proliferated singnicantly.

The large microbial diversity changes over different locations in our home, i.e. we will not find the same microorganisms in bed than in the bowl of the toilet. For example, in our kitchen, depending on the place that we examine, we find greater abundance of specific bacterium or other. In the image bottom, us show as in the stove of our kitchen find more Salmonella sp than Clostridium sp.

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Differences in the abundance of bacteria depending on the location (Image: G.E. Flores)

Even so, we can found a certain pater in this distribution, i.e. the microorganisms that inhabit certain areas are more similar than the comminities that we found in other locations. In the following dendogram we can observe that microorganisms found in our pillowcase are very similar to those that found in toilet, but completely different from whichwe can find in our kitchen cutting board.

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Dendrogram of similarity between the bacterial communities of various areas of our home. (Image: Robert, D. Dunn).

But, what is the reason for this geographical distribution?

The response is found in the differents emission sources of these organisms. Depending on the source we can find find a few species or others. Obviously the main microorganism source of emission  into the environment are humans. We know that millions of bacteria and other microorganisms live in our body and they spread everywhere, either by respiratory activity, waste digestion or skin contact. Each human leaves a specific microbial fingerprint in those places. 

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Major sources of emissions according to the area of the home to examine. See is that the largest source of emission are the own human. (Image: G. E. Flores)

In the graphic you can see that in some places appear microorganisms related to our intestines, specifically those who are ejecting with droppings. Is not wash you hans after going to the service, surely yo go spreading faecal bacteria everywhere. Also, if you pull the string with the toiled lid open, it causes the expansion of faecal bacteria as if it were a spray, reaching our toothbrushes  or the hand soap.

On the other hand, microbial diversity is very influenced by the number and type of home occupants. We cannot found the same microorganisms in a house with two persons than in other one with a family of seven. In addition, is has observed that not found the same microorganisms in homes where there is greater number of women that in which there is greater numer of males. Usually, mens released more microorganisms to environment.

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Graphic of the influence of the genre of the occupants in the diversity of microorganisms in our home (Image: Albert barberán).

Another important factor that determines this geographical distribution and microbial diversity is the presence of pets. If in our homes we have animals like cats or dogs, we will found more varied microbial communities. In these case, these microorganisms are related to feces, skin and glans of these animals.

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Differences in the abundance of certain bacterial species based on the presence or absence of pets (Image: Albert barberán).

Although the main source of emission are the occupants of these homes, microscopic comminities that colonise all corners are closely related to which we can found on the outside. In the case of fungi, this relationship is more narrow that in the case of bacteria. Even so, it has been observed that species are more varied in houses.

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Comparison of the rich bacterial and fungal of our homes and the foreign. (Image: Albert barberán)

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How much reason have the phrase “as my home any place! Each home is indeed aunique and specific universe of microscopic communities. There aren’t two equal in the world!

REFERENCES

Maribel-anglès

Knowing fossils and their age

In All You Need Is Biology we often make reference to fossils to explain the past of living beings. But what is exactly a fossil and how is it formed? Which is the utility of fossils? Have you ever wondered how science knows the age of a fossil? Read on to find out!

WHAT IS A FOSSIL?

If you think of a fossil, surely the first thing that comes to your mind is a dinosaur bone or a petrified shell that you found in the forest, but a fossil is much more. Fossils are remnants (complete or partial) of  living beings that have lived in the past (thousands, millions of years) or traces of their activity that are preserved generally in sedimentary rocks. So, there are different types of fossils:

  • Petrified and permineralized fossils: are those corresponding to the classical definition of fossil in which organic or hollow parts are replaced with minerals (see next section). Its formation can leave internal or external molds in which the original material may disappear.

    cangrejo herradura, fósil, cosmocaixa, mireia querol rovira, horseshoe crab
    Petrified fossil of horseshoe crab and its footsteps. CosmoCaixa. Photo: Mireia Querol Rovira
  • Ichnofossils (trace fossils): traces of the activity of a living being that are recorded in the rock and give information about the behavior of the species. They may be changes in the environment (nests and other structures), traces (footprints), stools (coprolites -excrements-, eggs …) and other traces such as scratches, bites…
    Cosmocaixa, huevos, dinosaurio, nido, mireia querol rovira
    Dinosaur eggs (nest). CosmoCaixa. Photo: Mireia Querol Rovira

    coprolitos, cosmocaixa, excrementos fósiles, mireia querol rovira
    Coprolites, CosmoCaixa. Photo: Mireia Querol Rovira
  • Amber: fossilized resin of more than 20 million years old. The intermediate state of amber is called copal (less than 20 million years) old. The resin, before becoming amber can trap insects, arachnids, pollen… in this case is considered a double fossil.

    Pieza de ámbar a la lupa con insectos en su interior. CosmoCaixa. Foto: Mireia Querol Rovira
    Piece of amber with insects inside, CosmoCaixa. Photo: Mireia Querol Rovira
  • Chemical fossils: are fossil fuels like oil and coal, which are formed by the accumulation of organic matter at high pressures and temperatures along with the action of anaerobic bacteria (bacteria that don’t use oxygen for metabolism).
  • Subfossil: when the fossilization process is not completed the remains are known as subfossils. They don’t have more than 11,000 years old. This is the case of our recent ancestors (Chalcolithic).

    Ötzi a subfossil. It is Europe’s oldest natural mummy. He lived during the Chalcolithic (Copper Age) and died 5300 years ago. Photo: Wikimedia Commons
  • Living fossils: name given to today’s living organisms very similar to species extinct. The most famous case is the coelacanth, it was believed extinct for 65 million years until it was rediscovered in 1938, but there are other examples such as nautilus.

    ammonites, nautilus, cosmocaixa, fósil, mireia querol rovira
    Comparison between the shell of a current nautilus (left) with an ammonite of millions of years old (right). CosmoCaixa. Photo: Mireia Rovira Querol
  • Pseudofossils: are rock formations that seem remains of living beings, but in reality they are formed by geological processes. The best known case is pyrolusite dendrites that seem plants. 
Infiltraciones de priolusita en piedra calcárea. CosmoCaixa. Foto: Mireia Querol
Pirolusita infiltrations in limestone. CosmoCaixa. Photo: Mireia Querol

Obviously fossils became more common after the appearance of hard parts (shells, teeth, bones …), 543 million years ago (Cambrian Explosion). The fossil record prior to this period is very scarce. The oldes tknown fossils are stromatolites, rocks that still they exist today formed by the precipitation of calcium carbonate because of the activity of photosynthetic bacteria.

The science of fossils is Paleontology.

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Stromatolite 2,800 million years old, Australian Museum. Photo: Mireia Querol Rovira

HOW A FOSSIL IS FORMED?

The fossilization can occur in five ways:

  • Petrifaction: is the replacement of organic material by minerals from the remains of a living being buried. An exact copy of the body is obtained in stone. The first step of petrificationis  permineralizationthe pores of the body are filled with mineral but organic tissue is unchanged. It is the most common method of fossilized bones).
  • Gelling: the body becomes embedded in the ice and don’t suffer transformations .
  • Compression : the dead body is on a soft layer of soil, such as clay, and is covered by layers of sediment .
  • Inclusion : organisms trapped in amber, or petroleum .
  • Impression: organisms leave impressions in the mud and the trace is preserved until the clay hardens.
    Fossilization processes and resulting fossils. Unknown author

    UTILITY OF FOSSILS

  • Fossils give us information on how living things were in the past, resulting in evidence of the biological evolution and help to establish the lineages of living things today.
  • Allow analyzing of cyclical phenomena such as climate change, atmosphere-ocean dynamics and even orbital perturbations of the planets.
  • Those who are of a certain age can be use to date the rocks in where they are found (guide fossils).
  • They give information of geological processes such as the movement of the continents, the presence of ancient oceans, formation of mountains…
  • The chemical fossils are our main source of energy .
  • They give climate information from the past, for example, studying the growth of rings in fossilized trunks or deposition of organic matter in the glacial varves.
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    Fossil trunks where growth rings are observed. American Museum of Natural History. Photo: Mireia Querol Rovira

    DATING FOSSILS

    To determine the age of fossils there are indirect methods (relative dating) and direct (absolute dating). As there is no perfect method and accuracy decreases with age, the sites are often dated with more than one technique.

    RELATIVE DATING

    The fossils are dated according to the context in which they are found, if they are associated with other fossils (guide fossils) or objects of known age and it depends on the stratum they are found.

    In geology, stratums are different levels of rocks that are ordered by their depth: according to stratigraphy, the oldest ones are found at greater depths, while the modern ones are more superficial, as the sediments have not had much time to deposit on the substrate. Obviously if there are geological disturbances dating would be wrong if there were only this method.

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    Stratigraphic timescale. Picture: Ray Troll

    ABSOLUTE DATING

    This methods are more accurate and are based on the physical characteristics of matter.

    RADIOMETRIC DATING

    They are based on the rate of decay of radioactive isotopes in rocks and fossils. Isotopes are atoms of the same element but with different number of neutrons in their nuclei. Radioactive isotopes are unstable, so they are transformed into a more stable ones at a rate known to scientists emitting radiation. Comparing the amount of unstable isotopes to stable in a sample, scientits can estimate the time that has elapsed since the fossil or rock formed.

    Carbon 14 cycle. Unknown author
    Carbon-14 cycle. Unknown author
  • Radiocarbon (Carbon-14): in living organisms, the relationship between C12 and C14 is constant, but when they die, this relationship changes: the uptake of C14 stops and decay with a descomposing rate of 5730 years. Knowing the difference between C12 and C14 of the sample, we can date when the organism died. The maximum limit of this method are 60,000 years, therefore only applies to recent fossils.
  • Aluminum 26-Beryllium 10: it has the same application as the C14, but has a much greater decaying period, allowing  datings up to 10 datings millions of years, and even up to 15 million years.
  • Potassium-Argon (40K/40Ar): is used to date rocks and volcanic ash older than than 10,000 years old. This was the method used to date the Laetoli footprints, the first traces of bipedalism of our lineage left by Australopithecus afarensis.
  • Uranium Series (Uranium-Thorium): various techniques with uranium isotopes. They are sed in mineral deposits in caves (speleothems) and in calcium carbonate materials (such as corals).
  • Calcium 41: allows to date bones in a time interval from 50,000 to 1,000,000 years .

PALEOMAGNETIC DATING

The magnetic north pole has changed throughout the history of Earth and its geographical coordinates are known in different geological eras.

Some minerals have magnetic properties and are directed towards the north magnetic pole when in aqueous suspension, for example clays. But when laid on the ground, they are fixed to the position that the north magnetic pole was at the time. If we look at what coordinates are oriented such minerals at the site, we can associate it with a particular time.

Deposición de partículas magnéticas orientadas hacia el polo norte magnético. Fuente: Understanding Earth, Press and Seiver, W.H. Freeman and Co.
Deposition of magnetic particles oriented towards the magnetic north pole. Source: Understanding Earth, Press and Seiver, W.H. Freeman and Co.

This dating is used on clay remains and as the magnetic north pole has been several times in the same geographical coordinates, you get more than one date. Depending on the context of the site, you may discard some dates to reach a final dating.

THERMOLUMINESCENCE DATING AND  OPTICALLY STIMULATED LUMINESCENCE (OSL)

Certain minerals (quartz, feldspar, calcite …) accumulate in its crystal structure changes due to radioactive decay of the environment. These changes are cumulative, continuous and time dependent to radiation exposure. When subjected to external stimuli, mineral emits light due to these changes. This luminescence is weak and distinct as apply heat (TL), visible light (OSL) or infrared (IRSL).

Fluorite's thermoluminescence. Photo: Mauswiesel
Fluorite’s thermoluminescence. Photo: Mauswiesel

Can be dated samples that were protected from sunlight and heat to more than 500 ° C, otherwise the “clock” is reset as the energy naturally releases.

ELECTRON PARAMAGNETIC RESONANCE (ESR)

The ESR (electro spin resonance) involves irradiating the sample and measuring the energy absorbed by the sample depending on the amount of natural radiation which it has been subjected during its history. It is a complex method which you can get more information here.

REFERENCES