A2: Microbes in the news

Article title: Behind the iron curtain: How the methan-making microbes kept early Earth warm Behind the iron curtain: How methane-making microbes kept the early Earth warm


Date: Arpil 17, 2017

Article author was not listed but the research’s author was: m S. Bray. The article was provided by the Georgia institute of Technology.

Source: Phys.org

Link: https://phys.org/news/2017-04-iron-curtain-methane-making-microbes-early.html

Assignment author: Morgen Southwood


Marcy Bray and his team simulated early earth conditions to try and explain why the oceans could be liquid in the first two billion years. The prevailing theory is that methanogens provided enough methane for the green house effect to maintain liquid oceans. The problem with this theory is that, as we learned in class, methanogenesis is an inefficient system, and can be out competed when alternatives are possible. One major competitor in this time period was the rust-breathing microbes, they would dominate any environment when iron was available. The term iron curtain, refers to the potential for rust-breathing microbes to repress methane emissions when rust is plentiful. If methane was completely suppressed then the planet would likely have cooled. The microbiologists simulated early earth to study microbial diversity and methane emissions in varying conditions. They found that in iron free pockets of the oceans, methanogens could have thrived and been enough of a source of methane for keeping early Earth warm.


This article strongly related to our lectures on the methane cycle It also related to some exam 1 material, when we learned about the ferrous and ferric iron signatures that signaled changes in early earth microbial diversity.

Critical analysis-

This article could have used some more explanations. I understood the conclusions it drew, but I wouldn’t have been able to without material I learned in this class. I would have needed someone to fill in the blanks for me. It was important to understand why rust-breathing microbes would have outcompeted methanogens, and the significance of shifts in microbial diversity with different conditions etc. The article assumed/required the reader to know this supplementary information, and therefore it was not accessible to the general public.  I think the article was scientifically accurate in the way it described the idea proposed by the results of the study, however the title is misleading. The title seems portray that the study was a confirmation, when it was only supportive of the idea.

Since I did have some background information, this article was very interesting to me. When I thought about the major shifts in microbial diversity of the planet , I always thought about microbes relating to oxygen. These rust breathing microbes and methanogens were just as important stepping stones in shaping the Earth.


The conclusion of the article is that methane emissions could have come from microbial communities that were in rust free patches of the ocean. I thought that the ocean was well mixed. How could there be sections of the early ocean that were so poorly mixed that they lacked iron, while other areas had high levels of iron?


1 Comment for “A2: Microbes in the news”



The article was intruging. I agree that the reader needed to speculate regarding the backround information that was not provided in the text.

As far as early Earth soils are concerned, I found a journal Article on the university library website titled , “Microbial Evidence for Fe(III) reduction on Early Earth,” by Vargas, et al. 1998, University of Massachusetts, Amherst. https://web.b.ebscohost.com.proxy.library.uaf.edu/ehost/pdfviewer/pdfviewer?sid=31b9749f-00b4-4bb8-a544-027eac15876b%40sessionmgr120&vid=4&hid=115

The authors suggest that early microbial respiration would have occurred in which anaerobic, hyperthermophillic bacteria reduced sulfur. However, according to geological chemistry, iron was most likely the first external electron acceptor. They also stated that during Early Earth, microbes would have had a limited number of electron acceptors available to them for respiration. Furthermore, Fe(III) was thought to be rather abundant on early Earth in archaeal seas and around hydrothermal vents on the ocean floor.

I’m not sure that my response actually answers your question, but it gives a bit of an insight into research carried out in Massachusetts in regards to different forms of microbial respiration and which of those microbes were more likely to reduce iron. Apparently, two species of hyperthermophilic microbes, onebacteria and one archaea, are able to reduce Fe(III) into magnetite when Fe(III) is introduced as an electron acceptor. (Vargas, et. al 1998.)

There is far more information in regards to why the authors decided to select one bacterial species, and one archaeal species in the paper. It’s a good read.