Featured Research

from universities, journals, and other organizations

Researchers Find Smallest Cellular Genome

Date:
October 14, 2006
Source:
University of Arizona
Summary:
The smallest collection of genes ever found for a cellular organism comes from tiny symbiotic bacteria that live inside special cells inside a small insect. Just 182 genes, the 160-kilobase genome could revise ideas about what's needed for a cell to work. The finding also provides new insight into bacterial evolution.

The bright yellow structure inside this newly hatched psyllid insect is the bacteriome, the special structure that houses endosymbiotic bacteria.
Credit: Nancy Moran, The University of Arizona

The smallest collection of genes ever found for a cellular organism comes from tiny symbiotic bacteria that live inside special cells inside a small insect.

The bacteria Carsonella ruddii has the fewest genes of any cell. The bacteria's newly sequenced genome, the complete set of DNA for the organism, is only one-third the size of the previously reported "smallest" cellular genome.

"It's the smallest genome -- not by a bit but by a long way," said co-author Nancy A. Moran, UA Regents' Professor of ecology and evolutionary biology and a member of the National Academy of Sciences. "It's very surprising. It's unbelievable, really. We would not have predicted such a small size. It's believed that more genes are required for a cell to work."

Carsonella ruddii has only 159,662 base-pairs of DNA, which translates to only 182 protein-coding genes, reports a team of scientists from The University of Arizona in Tucson and from Japan.

The finding provides new insights into bacterial evolution, the scientists write in the Oct. 13 issue of the journal Science.

Atsushi Nakabachi, a postdoctoral research associate in UA's department of ecology and evolutionary biology and a visiting scientist at RIKEN in Wako, Japan, is the first author on the research report, "The 160-kilobase genome of the bacterial endosymbiont Carsonella." The research was conducted in senior author Masahira Hattori's laboratory in Japan and in Moran's lab at the UA.

A complete list of authors is at the bottom of this release. The Ministry of Education, Culture, Sports, Science and Technology of Japan funded the work.

Many insects feed on plant sap, a nutrient-poor diet. To get a balanced diet, some sap-feeders rely on resident bacteria. The bacteria manufacture essential nutrients, particularly amino acids, and share the goodies with their hosts.

In many such associations, the bacteria live within the insect's cells and cannot survive on their own. Often the insect host cannot survive without its bacteria, known as endosymbionts.

The relationship between some insects and their endosymbionts is so close and so ancient that the insects house their resident bacteria in special cells called bacteriocytes within specialized structures called bacteriomes.

Studying the genomes of such endosymbionts can provide clues to how microorganisms' metabolic capabilities contribute to both their hosts and to biological communities.

An organism's genome, its complete complement of DNA, provides the operating instructions for everything the organism needs to do to survive and reproduce.

Endosymbiotic bacteria live in an extremely sheltered world and have a pared-down lifestyle, so they need a simpler set of instructions. Many of the metabolic pathways that free-living bacteria maintain have been lost after so many generations of living within insects.

Nakabachi and Hattori were interested in sequencing the genome of the bacteria Carsonella.

Moran had done some previous work on the Carsonella genome and found its DNA composition and evolution to be unusual. She suggested the team pursue the Carsonella that lived inside an Arizona psyllid insect called Pachypsylla venusta. The insect has only one species of endosymbiotic bacteria, which would simplify the genomic analysis.

The researchers collected Pachypsylla venusta psyllids from hackberry trees (Celtis reticulata) on the UA campus and around Tucson. The team extracted the Carsonella DNA and sequenced it.

Even though endosymbionts need fewer operating instructions to survive, the bacteria's itsy bitsy genome was a surprise.

"It lost genes that are considered absolutely necessary. Trying to explain it will probably help reveal how cells can work," said Moran, who is a member of UA's BIO5 Institute.

The scientists speculate that in the bacteria's evolutionary past, some of its genes were transferred into the insect's genome, allowing the insect to make some of the metabolites the bacteria needed. Once the insect shouldered those responsibilities and provided the bacteria with those metabolites, the bacteria lost those genes.

Animal and plant cells have specialized structures inside them called organelles that are derived from symbiotic bacteria that became incorporated into the cell over the course of evolution.

Carsonella's stripped-down genome may indicate that it is on its way to becoming an organelle, the researchers write in their article.

Authors on the paper are: Atsushi Nakabachi of the UA and RIKEN; Helen E. Dunbar and Nancy A. Moran of the UA; Atsushi Yamashita and Hidehiro Toh of Kitasato University in Sagamihara, Japan; Hajime Ishikawa of The University of the Air in Mihama, Japan; and Masahira Hattori of The University of Tokyo in Kashiwa, Japan and RIKEN Genomic Sciences Center in Yokohama, Japan.


Story Source:

The above story is based on materials provided by University of Arizona. Note: Materials may be edited for content and length.


Cite This Page:

University of Arizona. "Researchers Find Smallest Cellular Genome." ScienceDaily. ScienceDaily, 14 October 2006. <www.sciencedaily.com/releases/2006/10/061012184647.htm>.
University of Arizona. (2006, October 14). Researchers Find Smallest Cellular Genome. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2006/10/061012184647.htm
University of Arizona. "Researchers Find Smallest Cellular Genome." ScienceDaily. www.sciencedaily.com/releases/2006/10/061012184647.htm (accessed July 28, 2014).

Share This




More Plants & Animals News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) Video provided by AP
Powered by NewsLook.com
Russia Saves Gecko Sex Satellite, Media Has Some Fun With It

Russia Saves Gecko Sex Satellite, Media Has Some Fun With It

Newsy (July 27, 2014) The satellite is back under ground control after a tense few days, but with a gecko sex experiment on board, the media just couldn't help themselves. Video provided by Newsy
Powered by NewsLook.com
Trees Could Save More Than 850 Lives Each Year

Trees Could Save More Than 850 Lives Each Year

Newsy (July 27, 2014) A national study conducted by the USDA Forest Service found that trees collectively save more than 850 lives on an annual basis. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins