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.

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.

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.

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.

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.

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.

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. 

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.

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.

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.

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

• Robert, D. Dunn. Home life: Factors Structuring the bacterial diversity found within and between homes.
• Albert Barberán. The ecology of microscopic life in household dust.
• Gilberto E. Flores. Microbial biogeography of public restroom surfaces.
• Cover Photo: Microbe.net

The Loch Ness Monster and Yeti: Do they exist?

The Loch Ness Monster, Yeti, Chupacabras, Bigfoot, Kraken… we’ve all heard about them once and we even doubted their (in)existence. What is the truth about these creatures? Are they real? If not, what answers gives science to refute it? Find out in this article.

CRYPTOZOOLOGY

Cryptozoology is a pseudoscience, uses scientific terms but is based on beliefs rather than evidence and does not use the scientific method. It tries to find animals that have not been confirmed by science, called cryptids. Usually are beings appeared in myths and legends, but also extinct species that it ensures they have been seen at present, as the thylacine or dinosaurs (non-avian ones). You just have to do a search in internet to find fake photos that won’t mislead the most gullible person, but when the stories are installed in the collective memory, supporters of cryptozoology increase.

The siren of Maracaibo, an internet viral cryptid. Despite being a sculpture of Juan Cabana, some people still believe in these fake beings. Photo: unknown

Cryptozoology usually tries to add features of real animals to cryptids to make them more credible, and even appropriates of the species discovered by biology (zoology), like when they say the Kraken is actually a giant squid.

THE LOCH NESS MONSTER

Nessie it is the most famous cryptid, a gigantic aquatic animal which is supposed to live in Loch Ness in Inverness, Scotland. As with all cryptozoological beings, evidence of their existence are fuzzy pictures and testimonies of sightings. Surely you’ve ever seen the most famous photo of the Monster:

The first photo of Nessie, shot in 1934, was considered (and is considered) an evidence of their existence. 60 years after, Chris Spurling confessed that it was a fraud. Photo: Marmaduke Wheterell

This one, like all photos of the monster, have been proved to have been farces and frauds. However, they continue to fuel the myth: the annual profit in this part of Scotland are of several million euros. It is  not surprising that many lakes around the world have their own monster like Nahuelito, Caddy, Champ, Manipogo, Ponik …

WHY THE LOCH NESS MONSTER CAN’T EXIST ?

• Its age: the first reference of a being in this lake dates back to 565. So today it would be… 1451 years old, much more than the oldest known animal: Ming the clam (507 years old). Or even more, as some cryptozoologists argue that it could be a plesiosaur or a similar animal (extinct over 65 million years ago) about 20 meters long and 10-20 tons.

  

  Or maybe it was just an otter… Photo: Jonathan Wills

• Origins: if it was an animal from the Age of Dinosaurs, or their descendants, it is impossible to have always lived in the lake, which was frozen since the last Ice Age until about 12,000 years ago. There are no ways of connection within the lake and the sea, there are no sightings of the montser outside the lake, so ti could never go out to the sea to feed, for example.  Assuming also Nessie was an aquatic reptile, his preference would be subtropical waters, not the cold waters of Inverness (6 ° C on average).

• Family of Nessies: the only possible explanation for the continued existence for thousands or millions of years, is that there are no one, but at least 100 individuals like Nessie to keep a viable population, according to population ecology. The minimum viable population is the smallest isolated population having 99% chance to stay alive for 1000 years (Shaffer, 1981). In addition, the Loch Ness is 56.4 km long and 226 m deep, there is an obvious lack of space for all of them (in addition to that sightings would constant).

• Lack of corpses: in the case that there was a group of plesiosaurs, sooner or later their bodies should appear in the bank and no one single corpse has been found.

  

  Elephant swimming. In 1933, the year with more sighntinghs, a circus toured the area. Its elephant apparently bathed in the lake several times. Photo: Jeremy Tucker

• Insufficient food: the lake is deep, long and narrow (32 km x 1.6 km). As the base of the food chain on Earth are plants, in aquatic areas are phytoplankton, algae and plants that can sustain herbivores and carnivores. Loch Ness has a little surface area exposed to the sun, so do not get enough sunlight to do a massive photosynthesis. In addition, the water is dark because has turf in suspension, preventing the existence of light from a few meters depth. It is so unproductive that it could not survive a predator of more than 300 kilos. Obviously, there are few animals that are totally insufficient  for feeding one or more animals of 20 tonnes.

  

  Food chain of a freshwater environment. The arrows indicate the direction of energy from one link to another. Picture: unknown

• Lack of evidence with the latest technologies: BBC has tracked the lake several times with sonar and satellite navigation technology with negative results. Neither mini-submarines or 24 hours webcams have found no sign of the monster.
  

  THE YETI, THE ABOMINABLE SNOWMAN

  The second most famous cryptid is a giant bipedal ape living in the Himalayas. Or in North America (Bigfoot), Canada (Sasquatch) Almasty (Russia), Hibagon (Japan), Yowy (Australia)… Like Nessie, Bigfoot moves millions of euros/dollars and each country has its own. Also is suggested that could be some kind of extinct hominid, a Neanderthal, a  Homo erectus or a Gigantopithecus .

  

  Photograph which revived the legend of the Yeti (1951). Photo: Eric Shipton

  As with all cryptids, evidences are based on eyewitness sightings, blurry photos or with doubtful origin. But in this case there are hair samples ensuring that belong to the Yeti. What science says ?

  DNA ANALYSIS

  The current understanding of genetics has allowed us to establish a more precise family relationships and identify living beings through analysis of DNA. So Bryan Sykes (Oxford University) led a study that analyzed more than 30 hair samples preserved in Buddhist temples, museums and private collections. Result: horsehair, bison, human, raccoon, cow, wolf, coyote… but none of the Yeti .

  The good news for zoology is that two hair samples match the DNA of a polar bear fossil, which could belong to a bear species unknown until now or a variety of polar bear of another color (golden-brown).

  

  The most famous photo of Bigfoot is a snapshot of a video taken by Patterson-Gimlin

  THE CHUPACABRAS

  The Chupacabras (“goat-sucker”) is supposed to be a creature that kills and sucks the blood of farm animals without spilling a drop. Definitions are multifarious, bright red eyes, scales, bipedal, spikes on the back… also alleged dead Chupacabras are reported:

  

  The alleged chupacabras carcasses are usually canines with scabies who have lost hair, raccoons, or in this case a flying fox. Photo: unknown

  The Chupacabras has the distinction of operating in latin countries: Venezuela, Puerto Rico, Mexico, Argentina, Spain, Chile… The alleged habitat of chupacabras clashes with biogeography: a branch of science that studies the distribution of living beings on our planet .

  Knowing a basics of biological evolution and climate we can think like biogeographers: species are distributed according to their habitat and have adapted to the different areas and climates. No one would think of a frog living in the Sahara desert, for example. But Chupacabras seems to not care: inhabits a huge variety of landscapes between two continents and several islands, but of course, has a predilection for Spanish-speaking places. Nothing to do with biology: it is the product of a legend of oral tradition.

  ZOOLOGY VS CRYPTOZOOLOGY

  In conclusion, zoology is the branch of biology that to certify that it has discovered a new species must:

  • Submit an holotype (a copy of the animal) to the scientific community ( natural history museums, university…) available to anyone concerned.
    
  • The holotype has to pass a DNA test .
    
  • The discovery must be published in a scientific journal with arbitration or peer review (method to validate the results of the investigation)
  • After validation, the species is classified following the rules of the taxonomy and systematics.

    We don’t need to invent strange creatures and discredit biology: nature is surprising enough to marvel us at new tangible species zoology keeps discovering and describing. Amazing animals like tardigrades, pyrosomida, the giant squid and deep-sea species, platypus and poisonous rats… and many others remaining to be discovered.

    REFERENCES

    • Chordá, Carlos, 2007. El yeti y otros bichos ¡vaya timo! Ed. Laetoli
    • Monstruo del Lago Ness: ¿Qué hay de verdad tras el mito?
    • Photos of the Loch Ness Monster, revisited
    • Is Loch Ness monster dead?
    • El monstruo del lago Ness en Magonia
    • El Yeti, ¿Una leyenda tirada por los pelos?
    • Cover picture: Loch Ness Monster figure in Scotland. Photo by Mireia Querol Rovira

Evolution for beginners

Biological evolution is still not well understood by general public, and when we speak of it in our language abound expressions that confuse even more how mechanisms that lead to species diversity work. Through questions you may have ever asked yourself, in this article we will have a first look at the basic principles of evolution and debunk misconceptions about it.

IS EVOLUTION REAL? IT IS NOT JUST A THEORY OR AN IDEA WITHOUT EVIDENCES?

Outside the scientific field, the word “theory” is used to refer to events that have not been tested or assumptions. But a scientific theory is the explanation of a phenomenon supported by evidence resulting from the application of the scientific method.

The scientific method. Image by Margreet de Heer.

Theories can be modified, improved or revised if new data don’t continue to support the theory, but they are always based on some data, repeatable and verifiable experiments by any researcher to be considered valid.

So few people (sic) doubts about the heliocentric theory (the Earth rotates around the Sun), or the gravitational theory of Newton, but in the popular imagination some people believe that the theory of evolution made by Charles Darwin (and Alfred Russell Wallace) is simply a hypothesis and has no evidence to support it. With new scientific advances, his theory has been improved and detailed, but more than 150 years later, nobody has been able to prove it wrong, just the contrary.

WHAT EVIDENCE WE HAVE THAT EVOLUTION IS TRUE?

We have many evidences and in this post we will not delve into them. Some of the evidence available to us are:

• Paleontological record: the study of fossils tell us about the similarities and differences of existing species with others thousands or millions old, and to establish relationships respect each other.
• Comparative anatomy: comparison of certain structures that are very similar between different organisms, can establish whether they have a common ancestor (homologous structures, for example, five fingers in some vertebrates) if they have developed similar adaptations (analogous structures, for example, the wings of birds and insects), or if they have lost their function (vestigial organs, such as the appendix).

Homologous organs in humans, cats, whales and bats

• Embryology: the study of embryos of related groups shows a strong resemblance in the earliest stages of development.
• Biogeography: The study of the geographical distribution of living beings reveals that species generally inhabit the same regions as their ancestors, although there are other regions with similar climates.
• Biochemistry and genetics: chemical similarities and differences allow to establish relationships among different species. For example, species closely related to each other have a structure of their DNA more similar than others more distant. All living beings share a portion of DNA that is part of your “instructions”, so there are also found in a fly, a plant or a bacterium, proof that all living things have a common ancestor.

IS IT TRUE THAT ORGANISMS ADAPT TO THE ENVIRONMENT AND ARE DESIGNED FOR LIVING IN THEIR HABITAT?

Both expressions, frequently used, mean that living beings have an active role to adapt to the environment or “someone” has designed them to live exactly where they are. It is a typical example of Lamarck and giraffes: as a result of stretching the neck to reach the higher leaves of the trees,  currently giraffes have this neck for giving it this use. They have a necessity, they change their bodies to success. It is precisely upside down: it is the habitat that selects the fittest, nature “selects” those that are most effective to survive, and therefore reproduce. It is what is known as natural selection, one of the main mechanisms of evolution. It needs three requirements to act:

• Phenotypic variability: there must be differences between individuals. Some giraffes necks were slightly longer than others, just as there are taller people than others, with blue or brown eyes.
• Biological fitness: this difference has to suppose an advantage. For example, giraffes with a slightly longer neck could survive and reproduce, while the others don’t.
  
• Heredity: these characters must be transmitted to the next generation, the offspring will be slightly different to that feature, while “short neck” feature transmits less and less.

The variability in the population causes individuals with favorable characteristics to reproduce more and pass on their genes to the next generation, increasing the proportion of those genes. Image taken from Understanding evolution

Over the years these changes are accumulated until the genetic differences are so big that some populations may not mate with others: a new species has appeared.

If you thought that this is similar to artificial selection that we do with the different breeds of dogs, cows who give more milk, trees bearing more fruit and larger, congratulations, you think like Darwin as it was inspired by some of these facts. Therefore, living beings are mere spectators of the evolutionary process, depending of changes in their habitat and their genetic material.

WHY ORGANISMS ARE SO DIVERSE?

Genetic variability allows natural selection act. Changes in the genetic material (usually DNA) are caused by:

• Mutations: changes in the genome that may be adverse or lethal for survival, indifferent or beneficial to survival and reproduction. If they have benefits, they will pass to the next generations.
• Gene flow: is the motion of genes between populations (migration of individuals allows this exchange when mate with others in a different population).
• Sexual reproduction: allows recombination of genetic material of different individuals, giving rise to new combinations of DNA.

Populations that have more genetic variability are more likely to survive if happen any changes in their habitat. Populations with less variability (eg, being geographically isolated) are more sensitive to any changes in their habitat, which may cause their extinction.

Evolution can be observed in beings with a very high reproduction rate, for example bacteria, since mutations accumulate more quickly. Have you ever heard that bacteria become resistant to our antibiotics or some insects to pesticides? They evolve so quickly that within a few years were selected the fittest to survive our antibiotics.

ARE WE THE MOST EVOLVED ANIMALS?

Theory of Evolution has various consequences, such as the existence of a common ancestor and that therefore, that we are animals. Even today, and even among the young ones, there is the idea that we are something different between living beings and we are in a special podium in the collective imagination. This anthropocentric thinking caused Darwin mockery and confrontations over 150 years ago.

Caricature of Darwin as an orangutan. Public domain image first published in 1871

We use our language to be “more evolved” as a synonym for more complex, and we consider ourselves one species that has reached a high level of understanding of their environment, so many people believe that evolution has come to an end with us.

The question has a mistake of formulation: actually evolving pursues no end, it just happens, and the fact that millions of years allows the emergence of complex structures, it does not mean that simpler lifeforms are not perfectly matched in the habitat where they are. Bacteria, algae, sharks, crocodiles, etc., have remained very similar over millions of years. Evolution is a process that started acting when life first appeared and continues to act in all organisms, including us, although we have changed the way in which natural selection works  (medical and technological breakthroughs, etc.).

SO IF WE COME FROM MONKEYS, WHY DO STILL MONKEYS EXIST?

The truth is that we don’t come from monkeys, we are monkeys, or to be more rigorous, apes. We have not evolved from any existing primate. As we saw in a previous post, humans and other primates share a common ancestor and natural selection has been acting differently in each of us. That is, evolution has to be viewed as a tree, and not as a straight line, where each branch would be a species .

First scheme of the evolutionary tree of Darwin in his notebook (1837). Public domain image.

Some branches stop growing (species become extinct), while others continue to diversify. The same applies to other species, in case you have asked yourself, “if amphibians come from fish, why are there still fish?”. Currently, genetic analyzes have contributed so much data that they make so difficult to redesign the classical Dariwn’s tree.

Classification of live organisms based on the three domains Archaea, Bacteria and Eukarya, data of Carl R. Woese (1990). Included in Eukarya there are the Protista, Fungi, Plantae and Animalia kingdoms. Image by Rita Daniela Fernández.

Evolution is a very broad topic that still generates doubts and controversies. In this article we have tried to bring to uninitiated people some basics, where we can delve into the future. Do you have any questions about evolution? Are you interested into a subject that we have not talked about? You can leave your comments below.

REFERENCES

• Darwin’s Tree of Life is a Tangled Bramble Bush
• Algunas reflexiones sobre la clasificación de los seres vivos
• Museos vivos. Evidencias de la evolución
• Las ideas en la ciencia: Teoría, hipótesis y leyes
• Frequently asked questions about evolution
• Brock et. al. 1999. Biología de los microorganismos. Ed. Prentice Hall.
• Massa, Renato. El origen de la vida. La evolución de las especies. Ed. Susaeta.
• Cover image