Science and technology play important roles in the nature and quality of our lives, so it is not surprising that as a society, we are increasingly challenged by problems that have a scientific component. Individual decisions about vaccines, regional choices about water availability, or global agreements about climate change all require that science have a voice during the decision-making process. The microbial sciences touch upon such a wide range of issues that scientists in those fields are particularly relevant to these discussions. If scientists do not participate in these dialogues, then others will fill the void and the information may not be accurate or science based. Scientists must communicate about science with public audiences in order for members of the public to make informed decisions about the complex issues that face us in our technologically advanced society.
Bacteria frequently grow in communities called biofilms, which are aggregates of cells and polymers. An example of a biofilm is the dental plaque on your teeth. BiofilmsÂ are medically important as they can allow bacteria to persist in host tissues and on catheters, and confer increased resistance to antibiotics and dessication. Therefore understanding how biofilmsÂ form is crucial for controlling microbial infections. An advance in our understanding of biofilms formation is the observation that filamentous phages help themÂ assemble, and contribute to their fundamental properties.
Pseudomonas aeruginosa is an important human pathogen which is a particular problem in patients with cystic fibrosis. The ability of this bacterium to form biofilms in the lung is linked to its ability to cause chronic infections. Pseudomonas aeruginosa biofilms contain large numbers of filamentous Pf bacteriophages (pictured). These virusesÂ lyse cells and release DNA, which becomes oneÂ component of the biofilm matrix.
Mixing supernatants of P. aeruginosa cultures with hyaluronan, which is present in airways of cystic fibrosis patients, resulted in the formation of a biofilm – in the absence of bacteria. AÂ major component of P. aeruginosa biofilms was found to be Pf bacteriophages. When purifed Pf bacteriophages were mixed with hyaluronan, biofilms formed. Similar biofilms also formed when theÂ filamentous bacteriophage fd of E. coliÂ was mixed with hyaluronan.Â Mixtures of Pf bacteriophages and various polymers (alginate, DNA, hyaluronan, polyethylene glycol) formedÂ liquid crystals (matter in a state between a liquid and a solid crystal).
Pf phages were detected in sputum from patients with cystic fibrosis, but not in uninfected patients. Addition of Pf phage to sputum from patients infected with P. aeruginosa made the samples more birefringent, a property of liquid crystals. Compared with a strain of P. aeruginosa that does not produce Pf phage, colonies of virus-producing strains formedÂ liquid crystals. These observations indicate that Pf phage help organize the bacteria into a biofilm matrix.
Some features of biofilms include their ability to adhere to surfaces, to protect bacteria from dessication, and to increase resistance to antibiotics. Addition of phage Pf increased biofilm adhesion and tolerance against dessication. Such additionÂ also made the biofilm more resistant to aminoglycoside antibiotics, because these were sequestered in the biofilm. No phage-mediated increased resistance to ciprofloxacin was observed, probably because this antimicrobial does not interact with polyanions of the biofilm as do aminoglycosides.
These results show that presence of bacteriophage in a biofilm of P. aeruginosa helps organize the matrix while contributing to some of its fundamental properties. It seems likely that filamentous phages of other bacteria will play roles in biofilm formation, suggesting that targeting the phages in these matrices could be effectie strategies for treating biofilm infections.
ASM Live will be broadcast from ICAAC/ICC 2015Â in San Diego, CA, where hostÂ Michael Schmidt, PhD, Professor and Vice Chairman of Microbiology and Immunology at the Medical University of South Carolina, and co-host ofÂ This Week in Microbiology, will interview researchers about their work.
Streaming will take place at theÂ San Diego Convention Center,Â Room 29B, and meeting registrants are encouraged to attend. You can watch ASM Live at microbeworld.org. Content will alsoÂ be archived immediately onÂ YouTubeÂ andÂ MicrobeWorldÂ for future viewing.
I usually don’t post TWiM episodes here, but #90Â has a lot of virology. In this episode, recorded in La Jolla, CA at the annual meeting of the Southern California Branch of the American Society for Microbiology, I first speak with Laurene Mascola, Chief of Acute Communicable DiseasesÂ at theÂ Los Angeles County Department of Public Health. Dr. Mascola talks about how Los Angeles county has prepared for an outbreak of Ebola virus. Next up is David Persing, Executive Vice President and Chief Medical and Technology Officer at Cepheid. His company has developed an amazing, modular PCR machine that is brining rapid diagnosis everywhere, including the United States Post Office.Â And it might even be available on your refrigerator one day.
One of my goals as a science communicator is to be Earth’s virology professor. To do this I teach an undergraduate virology course at Columbia University and atÂ iTunes University. This past summer I ported my undergraduate virology course to Coursera.org where I reached 26,000 students. My next virology course at Coursera, How viruses cause disease, begins on 9 January 2014.
How viruses cause diseaseÂ explores the interplay between viruses and their host organisms. The course begins with an overview of how infection is established in a host, then moves to a virologist’s view of immune defenses. Â Next we consider how the replication strategy and the host response determine the outcome of infection, such that some are short and others are of long duration. The mechanisms by which virus infections transform cells in culture are explored, a process that may lead to tumor formation in animals. We then move to a discussion of how viral infections are controlled by vaccines and antiviral drugs. After an introduction to viral evolution, we discuss the principles learned from zoonotic infections, emerging infections, and humankind’s experiences with epidemic and pandemic viral infections. The course ends with an exploration of unusual infectious agents such as viroids, satellites, and prions, followed by a discussion of the causative agent of the most serious current worldwide epidemic, HIV-1.
To create the Coursera courses, I divide the lecture videos from my undergraduate offering into 10-20 minute segments. I add annotations to indicate parts of the illustrations that I highlight during each lecture. Questions are also inserted in the videos to ensure that students are learning the desired principles. Weekly quizzes, a final exam, and discussion forums round out the Coursera experience.
Because others might benefit from the shorter videos, I have also made them available at YouTube. These videos are annotated, but do not have the built-in questions which are only available on Coursera. I would be pleased to learn how to add questions to YouTube videos.
On episode #252 of the science show This Week in Virology,Â the complete TWiV team reads email from listeners about anti-vaccine activists, a career in microbiology, placentas, a virology textbook, the HeLa cell genome, norovirus, and much more.
You can find TWiV #252 at www.microbe.tv/twiv.