Marine bacteria undergo several
stressors in the marine environment such as change in temperature, salinity, pH,
oxygen, nutrient availability, etc. To overcome them, bacteria have developed
new strategies for adaption by synthesising substances called secondary
metabolites. Studies mentioned by Fernandes (2010) agree that secondary metabolites
are in fact produced by microbes after being derived from several algae and
invertebrates.
The need to study the
advantageous features of secondary metabolites according to Fernandes (2010)
has been triggered by the need for antibiotics against resistant strains, anti-
tumour and anti-cancer properties. To achieve the aim of the paper, they chose
fast growing strains, as laboratory conditions can never mimic natural
conditions. A molecular approach was employed as it showed to have a much
larger diversity and difference in count of diversity of bacteria compared to
the culture method.
Secondary metabolites include siderophores, that are
stable low molecular weight molecules
(0.4–1.5 kDa) with strong iron-binding capabilities. These are synthesized
as a response to low iron levels in the sea. They have several applications in
terms of medicine, as iron withdrawal is a suitable approach for illnesses such
as breast cancer, malaria, microbial infection, rheumatoid arthritis, cardiac
poisoning, solid tumors, hematological malignancies and aluminium related
pathologies (Fernandes, 2010).
Maintaining membrane fluidity by
altering fatty acids saturation (homeoviscous adaptation) has also observed in
bacterial membranes. A paper mentioned in Fernandes (2010), studies how decrease
in the fluidity of the cell membrane and an increase resistance to bursting
under osmotic stress can be achieved when there is an increase in saturation
degree of the membrane lipids of bacteria. Short term responses such as
shortening of the fatty acids in lipid A has been observed in mesophilic
bacteria during a cold stress. As a long-term response, cryophiles tend to integrate fatty acids to maintain
membrane fluidity.
Hopanoids (except the family Methylococcaceae) are metabolites that also aid in maintaining
membrane fluidity by increasing cell permeability and decreasing the diffusion of ions across the cell membrane. Studies have showed
that hopanoid content increases in response to environmental stress (Fernandes, 2010) .
Bacteria produce substances
called exopolysaccharides under low nutrient levels or when in stationary
phase, that have many functions including protection, stabilization and
storage. When bacteria strains were isolated from hydrothermal vents, they were
found to be useful in tissue regeneration and for the treatment of cardiovascular
and oncological diseases (Fernandes, 2010) . V. diabolicus produces an unusual EPS found to be a strong
bone-healing material. When A. infernus had its EPS modified to meet desired properties, it presented anticoagulant properties. This
shows that by altering the EPS we can achieve specificity, improve their
functions and create microenvironments around the cell membrane (Fernandes, 2010) .
Another secondary metabolite are
structures called terpenes, but not much is known about marine terpenes. Their general role includes inducing positive interactions between organisms
and their physiological functions.
Through the process of quorum
sensing by
bacteria (eg – Vibrios) i.e.
releasing of chemical inducers (metabolites) via a density dependent manner,
biofilms are formed. Its matrix can bind, concentrate certain metal ions and also help in
releasing them. Chemical resistance can aid biofilms to tackle predators.
Although the paper does give us
an insight to some of the secondary metabolites produced by marine bacteria and
how they use them under stressful conditions, it would be equally interesting
to understand what molecular techniques were used, as it was only briefly
mentioned. As this paper is a comprehensive review, they have drawn upon recent
and relevant material and so it does a good job of informing the reader about
the metabolites, its role in nature and in the marine environment, and its
potential therapeutic uses.
This paper creates a good base
for future research as the metabolites mentioned in the paper can be studied
further giving rise to potentially more/new benefits. For this, I think the
actual metabolite i.e. its morphology and properties, need to be taken into
account.
Bibliography
Fernandes, C. C. (2010). Production of Metabolites
as Bacterial Responses to the Marine Environment. Marine Drugs, 8(3), 705-727. http://www.mdpi.com/1660-3397/8/3/705/htm
Hi Ankitha,
ReplyDeleteThis paper adds to my interest on how Bacteria produce different secondary metabolites or substances that contain medicinal properties and therefore aid us in our health. I think this is a very important aspect in scientific research.
The paper mentions that Bacteria have homeoviscous adaptation in their membranes that under osmotic stress can stop bursting and that metabolites also aid this adaptation. However, with the responses, did the paper state or what do you think could be the cause or cue of either the short-term and long-term responses to occur? Do the bacteria choose which response or is it a natural process? Also could you explain what cryophiles are?
I really like how this paper describes some of the secondary metabolites produced and their function under different environmental stresses. For me, it could relate, in future, to environmental changes induced by events, such as climate change or even increased pollution toxicity. Such events causing increased CO2, anthropogenic matter and lack of nutrients that can adjust the environment these bacteria are found in, maybe even effecting extremophiles. This could lead to questions, such as, could our medicinal research change, negatively or positively, as a result of these Bacterial adaptation enhancements or loss? Maybe this could also give more insight into the specific roles of terpenes, along with further work into metabolites morphology and properties, as you state. Or do we just not have the technology to study terpenes. What do you think?
Thank you.
Sophie,
Hi Sophie,
DeleteThis paper was a review of several other papers and didn't go through certain things in detail.
Just to recap, homeoviscous adaptation is when saturated and long chain fatty acids are incorporated into phospholipid layers in order to maintain constant membrane fluidity. The membrane viscosity effects the general signalling pathways as well as homeostasis.
From what I understand, the process of homeoviscous adaptation is coordinated with several stressors such as hypoxia, osmotic stress, oxidative stress and temperature (hot or cold) stress. Different stressors work at different rates - response to hypoxia accumulates over time, once the cell has enough information about oxygen availability; response to temperature is a type of collective adaptation.
To answer your second question; it isn’t very clear whether this type of adaptation is natural or not. In my opinion, they possess this characteristic due to changing environmental conditions and to meet climatic demands. Had the environment not changed, they wouldn’t need to alter their membrane fluidity and could possibly invest their energy in a different function. I guess it also helps them explore different niches to avoid competition, etc.
Cryophiles are organisms, mainly bacteria, that can withstand severe cold temperatures.
You are right! The changing environment does make me think about how much less or more effective these bacteria could be in terms of their functions.
Honestly, I think it could go either way. Bacteria could produce less metabolites, maybe due to their investment in other biological functions. Some may benefit from global warming and produce more or different metabolites (future research area?).
Terpenes - are natural metabolites isolated from plants (originally). It has its use in foods, cosmetics, pharmaceuticals and other biotech applications. Marine terpenes (phomactins and peribysins) are found in fungi. A paper by Ebel (2010) looks at the structural diversity of marine terpenes. Carotenoid is a common type of terpene and it has its function in aiding fungi survive harsh conditions as they possess oxygen quenching qualities. They can eliminate free oxygen radicals and prevent oxidative stress. I think that the technology is available but there haven’t been many marine terpenes identified so further isolation would be necessary to comment on the metabolite on a whole.
I hope this helps.
Thank you for your thought!
Ankitha
The references I used -
Ebel, R. (2010). Terpenes from Marine-Derived Fungi. Marine Drugs, 8(8), 2340–2368. http://doi.org/10.3390/md8082340
Sinensky, M. (1974). Homeoviscous Adaptation—A Homeostatic Process that Regulates the
Viscosity of Membrane Lipids in Escherichia coli. Proceedings of the National Academy of Sciences of the United States of America, 71(2), 522–525.
Robert Ernst, C. S. (2016). Homeoviscous Adaptation and the Regulation of Membrane Lipids. Journal of Molecular Biology, 428(24), 4776–4791. http://www.sciencedirect.com/science/article/pii/S0022283616303084
Hey Ankitha
DeleteThat was very interesting to read and clears those that I was struggling to understand so thank you for that extra details, I learnt new things.
Thank you,
Sophie,
Hey Ankitha
ReplyDeleteIt is very interesting to see how bacteria adaptive feature turns out to be potentially very beneficial for human needs, and what are your thoughts on raising this bacteria in lab, will it change its properties, will it be even possible to culture this for future medicine?
thankyou
Hafizh
Hello Hafizh,
DeleteThe paper I have reviewed is a review of several other papers. The information they have acquired have been from primary literature so it is safe to say that the authors (of the papers used) were able to culture the bacteria and persisted them to release these metabolites to be analysed and quantified. The properties would have therefore been derived as a result of their experiment.
As far as application in medicine goes, I think the properties of the actual metabolite needs to be taken into ( as I mentioned ) to be able to widen its use.
Hope this answered your question.
Thanks,
Ankitha