Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. Earth Science News .




FLORA AND FAUNA
How quickly can a bacterium grow?
by Anne Trafton for MIT News
Boston MA (SPX) Sep 09, 2013


The finding suggests that bacteria could grow dramatically faster than they do now and still obey the second law of thermodynamics.

All living things must obey the laws of physics - including the second law of thermodynamics, which states that the universe's disorder, or entropy, can only grow. Highly ordered cells and organisms appear to contradict this principle, but they actually do conform because they generate heat that increases the universe's overall entropy.

Still, questions remain: What is the theoretical threshold for how much heat a living cell must generate to fulfill its thermodynamic constraints? And how closely do cells approach that limit?

In a recent paper in the Journal of Chemical Physics, MIT physicist Jeremy England mathematically modeled the replication of E. coli bacteria and found that the process is nearly as efficient as possible: E. coli produce at most only about six times more heat than they need to meet the constraints of the second law of thermodynamics.

"Given what the bacterium is made of, and given how rapidly it grows, what would be the minimum amount of heat that it would have to exhaust into its surroundings? When you compare that with the amount of heat it's actually exhausting, they're roughly on the same scale," says England, an assistant professor of physics. "It's relatively close to the maximum efficiency."

England's approach to modeling biological systems involves statistical mechanics, which calculates the probabilities of different arrangements of atoms or molecules. He focused on the biological process of cell division, through which one cell becomes two. During the 20-minute replication process, a bacterium consumes a great deal of food, rearranges many of its molecules - including DNA and proteins - and then splits into two cells.

To calculate the minimum amount of heat a bacterium needs to generate during this process, England decided to investigate the thermodynamics of the reverse process - that is, two cells becoming one. This is so unlikely that it will probably never happen. However, the likelihood of it happening can be estimated by aggregating the probabilities of reversing all of the smaller reactions that take place during replication.

One of the common reactions that occur during replication is formation of new peptide bonds, which form the backbone of proteins. Spontaneously reversing that type of reaction would take about 600 years, England says. The number of peptide bonds in a typical bacterium is about 1.6 billion, and the heat wattage needed to break all of those bonds is about 100 billion natural units.

"I would have to wait a really long time to see all of those bonds fall apart," England says.

By estimating the waiting time needed to observe a spontaneous reversal of replication, England calculated that the minimum amount of heat a bacterium needs to generate as it divides is a little more than one-sixth of the amount an E. coli cell actually produces during replication.

The finding suggests that bacteria could grow dramatically faster than they do now and still obey the second law of thermodynamics. England says that because cell replication is just one of the many tasks E. coli need to perform, it's unlikely they would evolve to their most efficient possible growth rate. However, for synthetic biology applications, it may be useful to create bacteria that can divide faster, which this paper shows is theoretically possible.

The paper may also offer some evidence for why DNA, and not RNA, evolved as the main form of genetic material, England says: DNA is more durable and doesn't spontaneously break its bonds as readily as RNA does. This means that RNA may have an advantage over DNA because it can grow faster and use up available resources. This supports a previously suggested hypothesis that RNA may have evolved first, before life arose on Earth, and DNA showed up later on.

"I think it's a helpful way of trying to get a little bit more of a handle on the different kinds of selection forces that may have been acting on [early] nucleic acids," England says.

He is now using the same theoretical approach to model how self-replicating cells evolve by working out new ways of adapting to environmental fluctuations.

.


Related Links
Massachusetts Institute of Technology
Darwin Today At TerraDaily.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





FLORA AND FAUNA
Giant Triassic amphibian was a burrowing youngster
San Diego CA (SPX) Sep 09, 2013
Krasiejow, Poland was a vastly different place 230 million years ago during the Triassic Period. It was part of a giant continent called Pangea, had a warm climate throughout the year, and was populated by giant amphibians that weighed half a ton and were 10 feet long. Metoposaurus diagnosticus was one of these giant amphibians, and its environment had only two seasons: wet and dry. Like m ... read more


FLORA AND FAUNA
Niger asks for foreign help for flood victims

Olympics: Tokyo 2020 is a bid in the shadow of Fukushima

Italy says Syria crisis to worsen refugee problem

Australian police arrest suspected people smugglers

FLORA AND FAUNA
U.S. Army Awards Lockheed Martin contract for Counterfire Radar Production

World's First Full Color 3D Desktop Printer Destined For High Schools

Lockheed Martin-Built A2100 Satellites: Over 400 Cumulative Years In Orbit And Counting

GSAT-7 Satellite Placed in Geosynchronous Orbit

FLORA AND FAUNA
Can we save our urban water systems?

Why does the area over southern high and sub tropical latitudes have more frequent and stronger rains?

Network of Unmanned Undersea Platforms Would Assist Manned Vessels

Eastern US water supplies threatened by a legacy of acid rain

FLORA AND FAUNA
East Antarctic Ice Sheet could be more vulnerable to climate change than previously thought

On warming Antarctic Peninsula, moss and microbes reveal unprecedented ecological change

Arctic Sea Ice Update: Unlikely To Break Records, But Continuing Downward Trend

West Antarctica ice sheet existed 20 million years earlier than previously thought

FLORA AND FAUNA
Study forecasts future water levels of crucial agricultural aquifer

An alga stressed by the light

S. Korea widens Japanese fish ban over contamination fears

Chinese dairies seek French tie-ups to shore up image

FLORA AND FAUNA
Japan scraps stranded tsunami ship

Lorena weakens into tropical depression off Mexico

Power outages, landslides after strong Guatemala quake

Monster volcano is one of the biggest in Solar System

FLORA AND FAUNA
Sudan bombs S. Sudan buffer zone position, kills 2: Juba

Origin of state of ancient Egypt given new time line

Defence chiefs meet over DR Congo conflict

Kenyan soldiers kill al-Shabaab guerillas

FLORA AND FAUNA
Hidden shell middens reveal ancient human presence in Bolivian Amazon

Look at what I'm saying

The true raw material footprint of nations

Researchers reveal hunter-gatherers' taste for spice




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement