In health and in disease - living together with microbes

Trillions of diverse microbes reside in our gut,  the gastrointestinal tract and as a community  collectively influence our state  of  health as well as  disease. This symbiosis  is not a recent phenomenon, says scientist Andrew Moeller who investigated the evolutionary histories of hominid gut microbiota for his doctoral thesis.  By the way microbiota  is the currently used terminology for a diverse microbial community in a given ecosystem and gut is one such ecosystem.  Acknowledging  the significant role of microbiota in human life, NIH, the National Institutes of Health, USA, initiated the ambitious Human Microbiome Project in 2008.   Microbiome is the word for the genomes of the microbial community in a given ecosystem.   Abbreviated as HMP, the project aims at, much like the earlier Human Genome Project, generating a   complete catalogue of the genomes of microbiota living in association with human body and analyse their role in human wellness and illness. 

  

Human digestive system: courtesy : wikipedia

Several very interesting pieces of information have come to light with regard to gut microbiota. Neonates beget a minimal share of maternal repertory, which gets enriched in diversity and proportion as the child grows and by  age 12 resembles the adult profile. Beyond age 70, there seems to be a decline in the  diversity and functional capabilities of the microbial community. Nature and nurture contribute to the diversity and functional capabilities  of microbiota. For example scientists suggest that the high fat high salt diet of the affluent west   and overuse of antibiotics elsewhere will leave telltale signs on the  gut microbial community Now the most important point:  the diversity and relative proportions of  microbiota is unique to each individual. In other words each of us have a unique microbial signature, a unique microbial identity.  According to experts this explains, to some extent,  individual preference / tolerance/intolerance  towards food/drug type.   

Thus by age 12 we achieve a unique balanced  microbial population in our gut.   Dysbiosis, that is  perturbations of this  balance   has been implicated in several intestinal and extra-intestinal disorders. For example in  a recent research paper Imhann et al reiterated  the role of dysbiosis  of  the gut microbiota  in inflammatory bowel disease (IBD). Others have found possible evidences to link allergy, asthma, metabolic syndrome, and even obesity. But the good news is that beneficial  microbial communities can be generated, cultivated and maintained  by consuming appropriate food. Probiotics which are fermented food items such as yoghurt, cheese, pickle etc. and prebiotics  fibre rich vegetables, fruits, cereals which ferment in the gut seem to aid this process greatly. 

TAILPIECE:
Does that mean gut feeling is just microbial biochemistry?

  

References:
1. Human intestinal Microbiome in health and disease:The New England Journal of Medicine:2016; 375:24
3. Diversity of the human intestinal microbial flora Science:2005; 10:1002-14
4. Gut microbiota composition correlates with diet and health in the elderly: Nature 2012, 488: 178-84 Claesson et al.
5.Diet rapidly and reproducibly alters the human gut microbiome: Nature 2014;505:559-63 David LA et al
6. The Gut microbiota in host health: a new clinical frontier: Gut 2016;65:330-9 Marchesi,JR et al.
7. Incorporation of therapeutically modified bacteria into gut microbiota inhibits obesity:J.Clinical Invest. :2014:124:3391-406. Chen Z et al
8. Interplay of host genetics and gut microbiota underlying the onset and clinical presentation of inflammatory bowel disease. Gut: 2018; 67: Imhan et al

When pushed to the extreme

Freezing, arid  terrain with sweeping winds: that is Antarctica, the southernmost continent on Earth.   Since the sighting of the ice mass in the first half of the nineteenth century by marine explorers,  Antarctica has attracted umpteen   expeditions. During the second half of twentieth century  extensive aerial surveys of the continent  were conducted mostly by the United States. Airplanes    carrying scientists and radar equipments criss-crossed over the icy continent. From the radar data   thickness of the ice cover  and presence of liquid water below the sheet could be estimated.   While those  old maps provide information on what the terrain was like "Then",    modern satellite imaging techniques yield detailed   "Now" images.

Antarctica with ice shelves marked-Courtesy Wikipedia

   

United States' National Science Foundation funds several projects on various aspects of Antarctica. Project Midas undertaken by UK    focuses on stability of Larson C ice shelf in West Antarctican coast. In addition to these two countries several others have  permanent research stations  there.  

Limacina Helicina Courtesy: Wikipedia

Not only penguins, blue whales and krill, Antarctica accommodates life in many other forms.  The terrain as such  is hostile; with  global warming and consequential increase in the acidity of the ocean   would it become even more inhospitable?   Tiny marine snails, Limacina Helicina (also called sea butterflies because evolution equipped them with wings rather than feet) have already devised a counter measure. Acidic ocean can leach out the protective coating on their outer shell. They have learnt to repair this damage not by regenerating the coating but by thickening the innerside of the shell by appropriate secretions. In the picture alongside, the white rectangle marks  the area where the effect of ocean acidification was studied. The antarctic fish Emerald rockcod too has braced itself against warming and acidity of the ocean, although it can take on only one at a time. 

  

Prof. Belinda Ferrari from the Australian Centre for Astrobiology recently recorded the ability of certain microbial communities to "live  on air alone".  These microbes  belonging to phyla Actinobacteria, can survive by oxidising trace amounts of atmospheric hydrogen and carbon monoxide, present in the atmosphere. Detailed genetic and biochemical studies showed that the microbes possess three very important enzymes: high-affinity hydrogenases, to  catalyse the reversible oxidation of hydrogen, carbon monoxide dehydrogenases to  facilitate the conversion of carbon monoxide to carbon dioxide and  CO2 fixation enzymes of the  RuBisCO family to   "fix" inorganic carbon into organic carbon. 

 Tailpiece:
Antarctic tourist season is from November to March, the summertime in southern hemisphere. 2016-17 clocked more than 44,000 visitors!

Blood Falls: Iron oxide stains the water flow
blood red in Taylor glacier
Courtesy:Wikipedia

References:
1. Flying lab to investigate Southern Ocean's appetite for carbon
2. Coping with climate stress in Antractica
3. Sea butterflies patch up shell damage from ocean acidification
4. Pteropods counter mechanical damage and dissolution through extensive shell repair
5. Scientists find antarctic microbes that live on air alone