Breaking News
March 23, 2018 - Mom’s Pre-Pregnancy Waist Size Tied to Autism Risk
March 23, 2018 - AMD Treat-and-Extend Regimens OK: Ophthalmology Times
March 23, 2018 - Safe-sleep recommendations for infants have not reduced sudden deaths in newborns
March 23, 2018 - Survey finds inappropriate prescribing of antibiotics for hospitalized children
March 23, 2018 - Researchers propose alternative treatment to target lymphoma signaling at its root
March 22, 2018 - Compound found in beet extract could help slow progression of Alzheimer’s disease
March 22, 2018 - Lower temperatures can trigger the body’s ‘good’ fat formation at cellular level
March 22, 2018 - Sentinel lymph node biopsies could be safely avoided for some breast cancer patients
March 22, 2018 - Combined Preeclampsia Test Superior to U.K. Standards
March 22, 2018 - Exclusive breastfeeding in hospital associated with longer breastfeeding duration
March 22, 2018 - Researchers prove link between common childhood cancer and inflammation
March 22, 2018 - Targeting aberrantly active telomerase to treat therapy-resistant melanoma
March 22, 2018 - California’s tax on millionaires yields big benefits for people with mental illness, study finds
March 22, 2018 - Weight-loss surgery reduces risk for severe chronic kidney disease and kidney failure
March 22, 2018 - Study identifies two genes associated with extreme nausea and vomiting during pregnancy
March 22, 2018 - Biohaven Enrolls First Patient In Phase 3 Clinical Trial To Evaluate Rimegepant Zydis® ODT In The Acute Treatment Of Migraine
March 22, 2018 - ‘Bionic Pancreas’ OK for Very Young T1D Patients
March 22, 2018 - Parkinson’s gene initiates disease outside of the brain
March 22, 2018 - NMSU researchers publish findings on effective measures to remedy stress among adolescents
March 22, 2018 - Immunotherapy combination increases overall survival in people with kidney cancer, study shows
March 22, 2018 - Gut microbiome may promote pancreatic cancer by inducing immune suppression
March 22, 2018 - New ocular inserts allow patient’s cornea to absorb more antibiotics
March 22, 2018 - FDA Alert: NeuroBlate Probe by Monteris Medical: Letter to Health Care Providers, Class I Recall
March 22, 2018 - Cessation of exercise can result in increased depressive symptoms
March 22, 2018 - Morning Break: Booze Study Brouhaha; Stem Cells for MS; Big Debt Problem
March 22, 2018 - New wearable tech from Western may hold big benefits for people with Parkinson’s
March 22, 2018 - Immune cells can repopulate in the retina after elimination, mice study shows
March 22, 2018 - States extend Medicaid for birth control, cutting costs — and future enrollment
March 22, 2018 - Research provides better understanding of how cancerous cells behave in low oxygen
March 22, 2018 - Menopausal hormone therapy taken soon after menopause may benefit the brain
March 22, 2018 - Booze Boosts Your Heart Rate
March 22, 2018 - Skeptical Cardiologist: Classifying Heart Failure
March 22, 2018 - Instead of nagging your spouse to lose weight, try going on a diet yourself
March 22, 2018 - Neem Biotech to share findings on cystic fibrosis biofilm disruption at ECFS Basic Science Conference
March 22, 2018 - Study uncovers new genetic cause of posterior polymorphous corneal dystrophy
March 22, 2018 - ENDO: Big Breakfast May Help in Diabetics
March 22, 2018 - I’m not overweight, so why do I need to eat healthy foods?
March 22, 2018 - UCLA-led study suggests unexpected reason for reduction in cardiovascular health disparities
March 22, 2018 - Study suggests detailed neuropsychological assessment for brief cardiac arrest survivors
March 22, 2018 - Anticoagulant drugs found safe to use in patients undergoing surgery for irregular heartbeat
March 22, 2018 - SP Industries appoints Brian Larkin as new President and CEO
March 22, 2018 - GTx Announced New Data Demonstrating Enobosarm’s Potential to Treat Stress Urinary Incontinence
March 22, 2018 - Higher Risk of Brain Deficits in Older Alcoholics
March 22, 2018 - Top US health official resigns in conflict of interest
March 22, 2018 - Study shows benefits of hair loss drug in improving cognitive function and vascular health
March 22, 2018 - Researchers explain link between 2 key Alzheimer’s proteins
March 22, 2018 - Patients on replacement therapy with thyroid hormone may have more comorbidities
March 22, 2018 - Higher online patient ratings linked to urologists who saw fewer Medicare patients
March 22, 2018 - FDA Approves Ilumya (tildrakizumab-asmn) for the Treatment of Moderate-to-Severe Plaque Psoriasis
March 22, 2018 - Beer Raises Heart Rate; KardiaBand Hyperkalemia Test; CHD Clinics
March 22, 2018 - A retinal implant that is more effective against blindness
March 22, 2018 - New system based on artificial intelligence provides reliable detection of breast cancer
March 22, 2018 - Research offers new understanding about cause of Parkinson’s disease
March 22, 2018 - HORIBA’s Microsemi CRP analyzer improves quality of care in emergency pediatric units, study shows
March 22, 2018 - Neuroscientists move closer to developing tools for deciphering brain function
March 22, 2018 - New test methods with less fear
March 22, 2018 - Range of Vaginal Dryness Products Can Help Postmenopausal Women: Study
March 22, 2018 - Higher Dose Tx Deemed Safe in Pulmonary TB
March 22, 2018 - Discovery of new ALS gene points to cytoskeleton as potential target for drug development
March 22, 2018 - Diet soda associated with higher odds of diabetic retinopathy
March 22, 2018 - LSD reduces ‘sense of self’
March 22, 2018 - Vitamin D deficiency linked to metabolic syndrome in postmenopausal women
March 22, 2018 - Changes in the intestines may be responsible for reversal of diabetes after bariatric surgery
March 22, 2018 - iPads and Cancer; Clot Retrieval and Stroke: It’s PodMed Double T!
March 22, 2018 - Premature births linked to changes in mother’s bacteria
March 22, 2018 - Brain SPECT scans predict treatment outcomes in patients with depression
March 21, 2018 - Researchers succeed in integrating artificial organelles into cells of living organism
March 21, 2018 - Researchers discover ‘missing mutation’ in severe infant epilepsy
March 21, 2018 - Researchers develop statistics-based computational scheme to zoom in on brain function
March 21, 2018 - Verge joins Genomics England’s Discovery Forum industry partnership
March 21, 2018 - Trovagene Announces First Patient Successfully Completes Cycle 1 of Treatment with PCM-075 in Combination with Low Dose Cytarabine (LDAC) in AML Trial
March 21, 2018 - Congenital Cardiac Cath Tx Often Strays from Guidelines
March 21, 2018 - Marked increase in cardiovascular risk factors in women after preeclampsia
March 21, 2018 - New app may help predict, track manic and depressive episodes in bipolar patients
March 21, 2018 - Discovery of genes could lead to development of novel therapies for EBV-related cancers
March 21, 2018 - High-fat, high-cholesterol diet depletes ranks of artery-protecting immune cells
March 21, 2018 - Research misconduct allegations shadow likely CDC appointee
March 21, 2018 - Most Breast Ca Patients Fail to Get Genetic Counseling
March 21, 2018 - Lopsided ear function can lead to lopsided brain development
March 21, 2018 - Acupuncture helps manage menopausal symptoms, review finds
Leaf-eating ability of beetle largely due to bacteria inside the insect

Leaf-eating ability of beetle largely due to bacteria inside the insect

image_pdfDownload PDFimage_print

A leaf-eating beetle has evolved a symbiotic relationship with bacteria that allows the insect to break down pectin — part of a plant’s cell wall that is indigestible to most animals.

The journal Cell published the findings on the novel function of the bacterium, which has a surprisingly tiny genome — much smaller than previous reports on the minimum size required for an organism not subsisting within a host cell.

“This insect is a leaf eater largely because of these bacteria,” says Hassan Salem, lead author of the study and a post-doctoral fellow in Emory University’s Department of Biology. “And the bacteria have actually become developmentally integrated into the insect’s body.”

Two organs alongside the foregut of the beetle Cassida rubiginosa house the bacteria and appear to have no other function than to maintain these microbes. “The organs are equivalent to the liver in humans, in the sense that they contain the tools to break down and process food,” Salem says.

The newly characterized bacterium has only 270,000 DNA base pairs in its genome, compared to the millions that are more typical for bacterial strains. That makes its genome closer to that of intracellular bacteria and organelles than to free-living microbes. Mitochondria, for example, the organelles that regulate metabolism within cells, have 100,000 base pairs.

Salem is a researcher in the lab of Emory biologist Nicole Gerardo, an associate professor who specializes in the evolutionary ecology of insect-microbe interactions. The lab combines genomic and experimental approaches to learn how both beneficial and harmful microbes establish and maintain relationships with their hosts.

A human gut holds about 10,000 species of bacteria. These microbial communities, which can be genetically characterized as microbiomes, are transferred generationally but are also dynamic and respond to environmental changes. The microbiome of an urbanite, for example, has different characteristics from that of a hunter-gatherer.

Unlike humans, insects tend to have specialized feeding ecologies. They offer simple models to study symbiotic relationships between microbes and their hosts.

Salem became fascinated by Cassida rubiginosa, more commonly known as the tortoise beetle, while he was a graduate student at the Max Planck Institute for Chemical Ecology in Jena, Germany. He was leafing through a 1953 edition of a book by the late Paul Buchner, a German scientist and one of the pioneers of systematic symbiosis research in insects. Buchner referenced a paper published in 1936 by one of his students, Hans-Jurgen Stammer, on Cassida rubiginosa.

“Stammer wrote that, unlike most leaf-eating beetles that he had studied, this one had sac-like organs that he had never seen before and the organs were filled with micro-organisms,” says Salem, who looked up Stammer’s original paper in a now-obscure journal. “He didn’t have the high-powered microscopes that we have now, or genome sequencing technology, so he wasn’t able to comment on the functionality of the mysterious microbes. At that point, the idea that microbes could do anything beneficial for an animal was mushy science.”

Intrigued by the article, Salem went to a nearby woodland to collect some of the leaf beetles. “To find these beetles, you don’t go looking for them,” he explains. “You go looking for the plants they eat.”

The tortoise beetle feeds on the tough, spiny leaves of the Californian thistle (Asteraceae). This prolific weed grows throughout much of the world and is difficult to control. “It pops up in a lot of areas where sheep are maintained,” Salem says. “In fact, it’s a huge pest to New Zealand sheep farmers. The more thistles covering a farmland, the less food the sheep have to eat and the lower the yield. But the thistle is hard to get rid of because its roots run so deep.”

Salem followed the trail of his curiosity to New Zealand, spending time with an agricultural researcher, Michael Cripps, who breeds the tortoise beetle as a bio-control model for thistles. “You drop 100 beetles on a thistle plant and the insects will just drain the plant metabolically until it dies,” Salem explains.

As an herbivore that specializes in eating leaves, the tortoise beetle must consume large amounts of plant cell walls, made of hard-to-digest materials like pectin. One of nature’s most complex polysaccharides, pectin is a gelatinous substance that gives plant cell walls their shape and rigidity. While it was unclear how the beetle obtained needed nutrients of amino acids and vitamins from such a diet, Salem suspected that symbiotic bacteria played a role.

When he joined the Gerado lab at Emory, Salem continued to study the tortoise beetle and its micro-organisms with the help of fellow post-doc Aileen Berasategui, a co-author of the Cell paper.

They used genome sequencing technology to characterize the microorganisms as a new species of bacterium. Despite its tiny genome, the bacterium has the power to degrade pectin.

“Just as an apex predator has claws and strong mandibles to obtain the nutritional value that it needs from its prey, the bacterium has pectin-digesting genes that enable the beetle host to deconstruct a plant cell,” Salem says.

After the bacterium breaks down the pectin, the beetle’s digestive system can then access all of the amino acids and vitamins within the plant’s cells for its nutrients.

Salem christened the new bacterium Candidatus Stammera capleta, after Hans-Jurgen Stammer, the ecologist who first glimpsed it and wondered about it more than 80 years ago.

“The most amazing thing to me is that we made this discovery because I read a really old book,” Salem says. “It speaks to the importance of natural history collections and libraries for old journals. We truly stand on the shoulders of giants, extending the work of those who came before us.”


Tagged with:

About author

Related Articles