mBiosphere

Monday, 21 September 2015 15:18

When too much of a good thing is a bad thing

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We’ve discussed the role of cyclic-di-GMP (c-di-GMP) in Pseudomonas biofilm formation on this blog recently. This type of modified nucleotide molecule acts as a second messenger (an amplified product that influences  phenotypes in response to stimuli) in many varied types of bacteria. Cyclic mono- and dinucleotides, such as cyclic AMP (cAMP) and c-di-GMP, are common secondary messengers.
Thursday, 17 September 2015 15:16

Small compound, big implications

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When walking by a pride of lions, I wouldn’t want to wear eau de antelope. Yes, the lions might decide to eat me anyway, but smelling like their favorite food wouldn’t do me any favors. This delicious type of camouflage is what the malaria parasite does after infecting its human hosts: it makes them smell more appealing to nearby mosquitos. The research behind this discovery was published in mBio by Megan Kelly and Dr. Audrey Odom this past spring.
The human microbiome is a collection of all the microorganisms living in association with the human body. This includes bacteria, viruses, eukaryotes, and archaea (single-celled prokaryotic organisms that are not bacteria or eukaryotes). In recent years, the human microbiome has been shown to play a role in various autoimmune diseases; the gut microbiome has been shown to play a role in obesity. Now, new research has demonstrated that the composition of the skin microbiome influences whether a person will clear infection by Haemophilus ducreyi.
Microbes may be single-celled life forms, but they can also work socially, as plenty of research has shown. Social behaviors may involve formation of a reproductive body, forming complex communities, or even altruistic behavior for the sake of the larger population. One of the first observations of social microbial interaction was in the now-famous quorum sensing of Aliivibrio fischeri, in which a bacterial population that has replicated to a certain density will change its gene expression pattern, and thus its behavior – in this case, turning on bioluminescence pathways that allow the colony to glow.
Friday, 11 September 2015 15:03

That'll do, (MRSA-covered) pig

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One of the most pressing scientific problems of our era is antibiotic resistance. After the golden era of antibiotic discovery, liberal use of these drugs in numerous settings has led to regular appearance of antibiotic-resistant outbreaks and 23,000 deaths in the US each year. The situation has become so dire that the President issued an Executive Order today, setting up a task force to revisit regulations of hospital, food, and farm use, calling for standardized practices across hospital settings.
The bacterium that causes cholera, Vibrio cholerae, can grow both aquatically and in a human host. To survive, the bacterium must be able to live in very distinct conditions: imagine how different the temperature, available nutrients, and neighboring microbes are between these two niches. To adapt, V. cholerae must turn on and off the genes appropriate for its current environment. How does the bacterial cell know what its current environment is and which genes it needs?
Wednesday, 26 August 2015 14:56

The anti-HIV properties of breast milk

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One of the most successful battles in the war on HIV has been stemming mother-to-child transmission of the virus. By treating expectant mothers with antiretrovirals that limit the virus numbers in the blood, HIV-infected women are able to have healthy, uninfected babies. However, babies are still susceptible to HIV virions that can be found in breastmilk, and breastfeeding is not recommended for new mothers in the U.S. Since these recommendations were made in the 1990s, infections passed to newborns right after birth have decreased 90% in the U.S.
Roughly 75% of all new, emerging, or re-emerging diseases affecting humans at the beginning of the 21st century are zoonotic diseases, meaning they originated in animals. For the past several years, researchers with the United States Agency for International Development’s PREDICT project have been working to discover and characterize viruses at the wildlife-human interface in order to be better prepared against future epidemics.
We’re approaching the end of summer, and many mBiosphere readers may want to take advantage of the hot weather to go hiking and camping before the chill of autumn sets in. But be prepared – in certain parts of North America, hikers are advised to wear protective clothing to help avoid tick bites, which may carry the causative agent of Lyme Disease, Borrelia burgdorferi. Where did this bacterium come from and why does it infect humans? In Applied and Environmental Microbiology this week, a new review by Dr. Nicholas Ogden et. al. covers the evolutionary and geographical history of Lyme…
Streptococcus species are a natural part of the microflora: its ability to survive under a variety of conditions allow it to colonize several niches on the human body. Some of these species live as mostly harmless commensals, while some of these are potential pathogens that can cause disease under the right circumstances. Group B Streptococcus (GBS), or Streptococcus agalactiae, falls under both categories, as healthy adults rarely present GBS disease symptoms, but those with immunocompromised immune systems – especially the very young and the elderly – can be susceptible to invasive disease.
Should infectious disease researchers be allowed to generate lab strains that are more pathogenic than naturally occurring microbes?
Lignocellulosic plant biomass is one of the most available and renewable materials on earth. It serves as a potent source of energy, being comprised of several polysaccharide sugars crosslinked to lignin. Sugars fermented into bioethanol can be used as a fuel source or additive.  But removing the polysaccharides and breaking them down into smaller sugar subunits requires heat, chemical, and enzymatic treatment, and is energetically and financially expensive.  Research on a wide variety of lignocellulose-degrading microbes, from archaea to bacteria to fungi, is therefore focused on finding a more efficient way to degrade these materials.
Friday, 14 August 2015 13:50

A role for histidine in influenza HA

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HA is a glycoprotein found in the viral envelope of influenza A virus as a trimer (see schematic at left). HA is required for the first step of the viral life cycle: attachment of the virus to its new host cell. After HA binds its sialic acid receptor, the host takes up the virus via endocytosis. As the endosome becomes acidic, HA changes shape to insert into the lipid membrane, fusing viral and endosomal membranes to release viral genomic contents into the cytoplasm (see schematic below). Because HA is so important for these steps in viral replications, understanding how it…
Wednesday, 12 August 2015 13:41

Special (drug) delivery

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Targeted drug delivery is the ultimate goal: imagine fewer side effects, more selective killing, and lower drug concentration needed to reach a desired effect. Toward that end, microbes are well ahead of us (as usual), having developed several targeted delivery systems.
Thursday, 06 August 2015 13:40

Learning what Listeria likes about lox

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Do you enjoy lox on your bagel? A refreshing ceviche in the hot summer weather?  New research published this week in Applied and Environmental Microbiology highlights the importance of proper storage of salmon and other meats that require no cooking prior to eating.
Thursday, 30 July 2015 13:34

Rethinking the cell wall

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Budding microbiologists learn that the cell wall of bacteria and fungi plays an vital structural role. Indeed, spheroplasts (cells that have had their walls removed) are easily lysed with water, unable to maintain osmotic stability. Part of the cell wall duty is to remain rigid and provide the cell shape – this is most obvious when seeing the round spheroplasts from a rod-shaped cell (pictured).
Tuesday, 28 July 2015 13:31

CF Microbes Survive with Little to No Oxygen

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On sabbatical four years ago, Dianne K. Newman, PhD, came up with an idea to apply geochemistry tools to infectious diseases. At that point Newman, a professor of biology and geobiology at the California Institute of Technology, already had been working in Pseudomonas biology for a decade, and her laboratory work suggested that some findings may be relevant in infectious diseases of the lungs, like cystic fibrosis (CF).
The doctor enters the patient’s room for the fourth visit in three days. Her immunosuppressed patient was transferred from a small local clinic to this large research facility to provide more intensive treatment. Despite this, the patient is deteriorating, and suffering from multiple infections. A culture has just come back from the microbiology lab, which shows the Klebsiella pneumoniae isolated from the patient is resistant to ertapenem, imipenem, and meropenem – the isolate is a carbapenem-resistant Enterobacteriaceae (CRE). The drug susceptibility testing directs therapeutic decisions, but an important question remains: did the patient pick up this resistant strain in this…
Thursday, 23 July 2015 12:53

Signaling a stop to biofilm formation

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Many reports focus on bacterial growth in water (especially nutrient-rich waste water), but bacteria also grow well – if not better – on surfaces, where they can form a biofilm community. Biofilms are surface-dwelling microbes growing in a single- or multispecies mixture, encased in an extracellular matrix. Scientists study many characteristics of biofilms – nutrient and oxygen gradation, gene expression patterns, adherence capabilities – but important to healthcare systems is the resilience of biofilms. Biofilms are extremely resistant to antibiotic treatment, and thus a common problem of hospital-acquired infections.
While many people think of the flu (influenza) as just a pesky illness, it can be lethal. The 1918 Spanish flu killed an estimated 50 to 100 million people. To protect against the morbidity and mortality from seasonal flu, each year scientists develop a vaccine to protect against the specific influenza strains that are predicted to cause the most problems for that year. Since future pandemics or outbreaks cannot be predicted, it has not been possible to make a protective pre-pandemic vaccine with current vaccine strategies. Now researchers say they have developed a strategy that may lead to a practical…

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