Microorganisms
clock | September 8, 2006Fifth in the five-part series on clocks in bacteria, covering more politics than biology (from May 17, 2006):
In the previous posts in this series, I covered the circadian clocks in Synechococcus, potential circadian clocks in a couple of other bacteria, and the presence of clock genes (thus potentially clocks) in a number of other bacteria. But what happened to the microbiological workhorse, the Escherichia coli? Does it have a clock? Hasn't anyone checked?
Believe it or not, this question is colored by politics. But I have to give you a little background first. Latter half of the 19th…
clock | September 8, 2006
Fourth in the five-part series on clocks in bacteria (from April 30, 2006):
For decades, it was thought that prokaryotes did not have circadian clocks. Then, a clock was discovered in a unicellular cyanobacterium, Synechococcus (later also in Synechocystis [1] and Trichodesmium [2]) which quickly became an important model in the study of circadian rhythms in general. Still, it was thought, for ten years or so, that no other prokaryotes had a circadian clock. Recently, the clock genes were found in filamentous (chain-forming) cyanobacteria, as well as a whole host of other bacteria and…
clock | September 7, 2006
The third installment in the five-part series on clocks in bacteria (from April 19, 2006):
As you probably know, my specialty are birds, so writing this series on clocks in microorganisms was quite an eye-opener for me and I have learned a lot. The previous two posts cover the clocks in the cyanobacterium Synechococcus elongatus, the first bacterium in which circadian rhythms were discovered and, thus, the species most studied to date.
The work in Synechococcus has uncovered a cluster of three genes - kaiA, kaiB and kaiC - that are essential for circadian rhytmicity in this species. kaiA…
clock | September 6, 2006A microbiological metaphor for the blogosphere (from November 27, 2005):
Heh! I always wanted to write this post. Being lazy is actually good sometimes. Just wait long enough and, lo and behold, someone else will write your post! Saves you time and energy.
Daniel Conover, whom I had great pleasure to meet in person at the ConvergeSouth conference, wrote a very thought-provoking post: Bacteria, blogs, holographic consciousness and The Singularity. There is a lot of biology there, but that is just a pretext for trying to understand what the Internet, and blogs in particular, are growing up to…
clock | September 6, 2006
Second post in a series of five (from April 05, 2006):
In the previous two posts, here and here, I have mentioned how the discovery of circadian clocks in Cyanobacteria changed the way we think about the origin and evolution of circadian clocks. Quite soon after the initial discovery, the team from Carl Johnson's laboratory published two papers [1,2] describing a more direct test of adaptive function of circadian clocks in the Synechococcus elongatus.
Wild-type and various clock-mutants in Synechoccocus, when raised in isolation in light-dark cycles, have comparable reproductive rates.…
clock | September 5, 2006
Hypotheses leading to more hypotheses (from March 19, 2006 - the Malaria Day):
I have written a little bit about malaria before, e.g, here and here, but this is my special Malaria Action Day post, inspired by a paper [1] that Tara sent me some weeks ago and I never got to write about it till now.
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In a journal called "Medical Hypotheses" Kumar and Sharma [1] propose that jet-lagged travellers may be more susceptible to getting infected with malaria. They write:
Rapid travel across several time zones leads to…
clock | September 5, 2006
First in a series of five posts on clocks in bacteria (from March 08, 2006)...
As I stated in the introductory post on this topic, it was thought for a long time that prokaryotes were incapable of generating circadian rhythms. When it was discovered, in 1994 [1], that one group of prokaryotes, the cyanobacteria, possess a circadian clock, the news was greeted with great excitement. This was the first definitive demonstration of a circadian clock in a bacterium (I intend to revisit the E.coli saga in a later post).
All three hypotheses for the origin of the circadian clock suppose that it…
clock | September 4, 2006From November 28, 2005, a post about teaching...
There has been literally an explosion of new knowledge about malaria in the last ten years or so. It is an amazing disease. Looking at all the new findings coming out almost every week makes me salivate because of...teaching! Malaria is a fantastic case-study to keep mentioning over and over again throughout the course. Let me backtrack for a moment....
I teach general biology to adult non-science majors at a community college. It is a speed course, lasting only eight weeks. In eight meetings, one has to deliver an enormous amount of material…
clock | September 4, 2006The first in a series of posts on circadian clocks in microorganisms (from February 23, 2006)...
Many papers in chronobiology state that circadian clocks are ubiqutous. That has been a mantra since at least 1960. This suggests that most or all organisms on Earth possess biological clocks.
In the pioneering days of chronobiology, it was a common practice to go out in the woods and collect as many species as possible and document the existence of circadian rhythms. Technical limitations certainly influenced what kinds of organisms were usually tested.
Rhythms of locomotor activity are the…
clock | September 2, 2006This week (Monday to Friday), at least in terms of reposting stuff from my old blogs (but hopefully also a couple of new posts), the theme will be Microorganisms.
In preparation for this, you may want to check my recent posts on biological clocks in Protista, sex life of Paramecium, a virus that made you smart and the ecology of Lyme Disease (oh, I forgot - I also hosted Animalcules #4). I hope you enjoy the series.
clock | July 4, 2006Writing a chronobiology blog for a year and a half now has been quite a learning experience for me. I did not know how much I did not know (I am aware that most of my readers know even less, but still....). Thus, when I wrote about clocks in birds I was on my territory - this is the stuff I know first-hand and have probably read every paper in the field. The same goes for topics touching on seasonality and photoperiodism as my MS Thesis was on this topic. I feel equally at home when discussing evolution of clocks. I am also familiar with the clocks in some, but not all, arthropods. And…