Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Microbial resident enables beetles to feed on a leafy diet

17.11.2017

Thistle tortoise beetles outsource the job of breaking down plant cell walls to a symbiotic bacterium. It provides the beetle with the enzymes required to break down certain plant cell wall components. The genome of the bacterium is the smallest ever sequenced of any organism living outside a host cell. It contains genes that are responsible for the production of pectinases, the enzymes that break down pectin, an essential component of the plant cell wall. The production of pectinases is therefore the primary function of these bacteria. Without bacterial symbionts the beetles could not to gain access to the nutrients inside the plant cells and hence would be unable to survive

An international team including researchers from the Max Planck Institute for Chemical Ecology has described a bacterium residing in a species of leaf beetles which has an unexpected feature: it provides the beetle with the enzymes required to break down certain plant cell wall components. The genome of the bacterium is the smallest ever sequenced of any organism living outside a host cell.


Fluorescence in situ hybridization (FISH): The cross-section shows the symbiotic organs associated with the gut of the beetle. In these sac-like reservoirs, the symbiotic bacteria (green) are housed.

Benjamin Weiss / Mainz University; Hassan Salem / Emory University


The thistle tortoise beetle (Cassida rubiginosa) feeds on thistle leaves. Its favorite food plant is the field thistle, a dreaded weed in agriculture worldwide.

Hassan Salem / Emory University

It contains genes that are responsible for the production of pectinases, the enzymes that break down pectin, an essential component of the plant cell wall. The production of pectinases is therefore the primary function of these bacteria. Without bacterial symbionts the beetles could not to gain access to the nutrients inside the plant cells and hence would be unable to survive (Cell, November 2017, doi 10.1016/j.cell.2017.10.029).

„The bedrock of our study were the histological descriptions and drawings of the beetle’s symbiotic organs that were first published by the German zoologist Hans-Jürgen Stammer more than 80 years ago. We wanted to molecularly characterize the extraordinary partnership between a leaf beetle and its symbionts described by Stammer as a rare peculiarity,” first author Hassan Salem, formerly a doctoral student at the Max Planck Institute for Chemical Ecology, explains. He is currently a Feodor Lynen Postdoctoral Fellow of the Alexander von Humboldt Foundation at Emory University in Atlanta, Georgia, USA.

Hans-Jürgen Stammer (1899-1968) studied symbiotic partnerships between insects and bacteria during the 1920s and 30s. He found that leaf beetles (Chrysomelidae) are notorious for not partaking in symbiotic partnerships. However, his studies also revealed that there were exceptions to this finding among some tortoise beetle species, such as the thistle tortoise beetle (Cassida rubiginosa). These tortoise beetles are equipped with unusual organs, which he described in a 1936 study.

The symbiotic bacteria reside in sac-like reservoirs in the guts of the beetles. Female beetles transfer the symbionts through vaginal tubes to their offspring by applying a tiny symbiont caplet to each egg. The hatching larvae eat through the egg shell and then consume the caplets containing the symbiotic bacteria.

Leaf beetles are able to degrade components of the plant cell wall, such as cellulose and pectin, with the help of digestive enzymes. However, genetic analysis showed that the thistle tortoise beetle lacks the genes that are responsible for the production of the respective enzymes (pectinases). The new study reveals that this deficit is compensated for by a close partnership with a bacterium that resides in special organs close to the beetle’s gut.

To understand the importance of the bacterial symbionts for the beetle, the authors conducted a range of bioassays, some that were combined with enzymatic measurements. “When we compared enzyme activity in tortoise beetles with and without symbiotic bacteria, we found that beetles without symbionts were not able to digest pectin in order to gain access to the nutrients in the cell and as a consequence their chances of survival decreased,” says Roy Kirsch from the Max Planck Institute for Chemical Ecology.

Genetic analysis of the symbiotic bacteria ̶ which the researchers present as “Candidatus Stammera capleta“ in their current study to honor Stammer’s observations ̶ uncovered another surprise: The genome of the microorganism is reduced to only a few hundred genes, among them some genes that regulate the production and transport of pectinases.

Accordingly, the genome is tiny: Containing only ~270.000 base pairs, the genome of the bacterium is the smallest ever described for an organism that exists outside a host cell. Escherichia coli bacteria in comparison ̶ bacteria that live inside the gut of many animals including humans ̶ have 4.600.000, or 17 times as many base pairs. Only some bacteria that are housed inside their hosts’ cells are known to have smaller genomes than the beetle symbiont.

The symbiosis between the beetle and its symbiont is characterized by a clear division of labor. “The beetle host possesses the genes responsible for producing cellulases to digest cellulose, whereas the symbiont provides the pectinases. Together they have the necessary enzymes to break down the plant cell wall. Especially notable is the fact that this is the first description of a specialized bacterial symbiont with a primary or even sole function dedicated to pectin degradation,” Hassan Salem summarizes.

That many herbivorous animals exist today is the result of adaptations that evolved over time. In fact, microorganisms have played a major role in many such adaptations. The thistle tortoise beetle is an impressive example. Without pectinases it would have no access to nutrients inside a plant cell. The production of these enzymes has been outsourced to a service provider: a bacterium living in special organs near its gut.

In many leaf beetle species, the genes that activate digestive enzymes for the degradation of plant cell walls originated from fungi and bacteria and were introduced into the genomes of the beetles’ ancestors via horizontal gene transfer. “It is fascinating that insects have solved the problem of how to break up plant cell walls so differently. Why some insects acquired genes from microbes horizontally, while others maintain symbionts to do the same job is an interesting question that remains to be answered in future studies,” says Martin Kaltenpoth from the University of Mainz.

Original Publication:
Salem, H., Bauer, E., Kirsch, R., Berasategui, A., Cripps, M., Weiss, B., Kogy, R., Fukumori, K., Vogel, H., Fukatsu, T., Kaltenpoth, M. (2017). Drastic genome reduction in an herbivore's pectinolytic symbiont. Cell 172, DOI: 10.1016/j.cell.2017.10.029
https://doi.org/10.1016/j.cell.2017.10.029

Further Informationen:

Dr. Hassan Salem, Department of Biology, Emory University, Atlanta, GA 30312, USA, E-Mail hssalem@emory.edu

Prof. Dr. Martin Kaltenpoth, Johannes-Gutenberg-Universität Mainz, Johann-Joachim-Becher-Weg 13, 55128 Mainz, Tel. +49 6131 3924411, E-Mail mkaltenp@uni-mainz.de

Contact and Media Requests:
Angela Overmeyer M.A., Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07743 Jena, +49 3641 57-2110, E-Mail overmeyer@ice.mpg.de

Download of high resolution images via http://www.ice.mpg.de/ext/downloads2017.html

Angela Overmeyer | Max-Planck-Institut für chemische Ökologie

More articles from Life Sciences:

nachricht Complete skin regeneration system of fish unraveled
24.04.2018 | Tokyo Institute of Technology

nachricht Scientists generate an atlas of the human genome using stem cells
24.04.2018 | The Hebrew University of Jerusalem

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: BAM@Hannover Messe: innovative 3D printing method for space flight

At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.

Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...

Im Focus: Molecules Brilliantly Illuminated

Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.

Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Quantum Technology for Advanced Imaging – QUILT

24.04.2018 | Information Technology

AWI researchers measure a record concentration of microplastic in arctic sea ice

24.04.2018 | Earth Sciences

Complete skin regeneration system of fish unraveled

24.04.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>