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Volume 6, Issue 4, pp. 184 - 211, April 2019

Issue cover
Cover: Microbial mats are multi-layered sheets of microorganisms, composed mainly of bacteria and archaea. The photograph shows patches of encrusting red and green algae lying beneath filamentous bacterial mats on rock surfaces (at East Diamante volcano, Mariana Islands, USA, 190 m/623 ft depth). The small white corals on the rocks are about 5 cm/2 in long. Thus, here the chemosynthetic and photosynthetic communities overlap (image by Submarine Ring of Fire 2004 Exploration, NOAA Vents Program); image modified by MIC. The cover is published under the Creative Commons Attribution (CC BY) license. Enlarge issue cover


Forty-five-year evolution of probiotic therapy

Scarlett Puebla-Barragan and Gregor Reid

page 184-196 | 10.15698/mic2019.04.673 | Full text | PDF | Abstract

In the past forty-five years, the field of probiotics has grown from a handful of laboratory studies and clinical ideas into a legitimate research and translational entity conferring multiple benefits to humans around the world. This has been founded upon three principles: (i) the need for alternatives to drugs that either have sub-optimal efficacy or severe adverse effects; (ii) a growing interest in natural products and microbes, in particular catalyzed by studies showing the extent of microbes within humans and on our planet; and (iii) evidence on the genetics and metabolic properties of probiotic strains, and clinical studies showing their effectiveness. While some manufacturers have sadly taken advantage of the market growth to sell supplements and foods they term probiotic, without the necessary human study evidence, there are more and more companies basing their formulations on science. Adherence to the definition of what constitutes a probiotic, conclusions based on tested products not generalizations of the whole field, and applications emanating from microbiome research identifying new strains that provide benefits, will make the next forty-five years significantly changed approaches to health management. Exciting applications will emerge for cardiovascular, urogenital, respiratory, brain, digestive and skin health, detoxification, as well as usage across the world’s ecosystems.

Research Articles

Chlamydia pneumoniae is present in the dental plaque of periodontitis patients and stimulates an inflammatory response in gingival epithelial cells

Cássio Luiz Coutinho Almeida-da-Silva, Tamer Alpagot, Ye Zhu, Sonho Sierra Lee, Brian P. Roberts, Shu-Chen Hung, Norina Tang and David M. Ojcius

page 197-208 | 10.15698/mic2019.04.674 | Full text | PDF | Abstract

Chlamydia pneumoniae is an airborne, Gram-negative, obligate intracellular bacterium which causes human respiratory infections and has been associated with atherosclerosis. Because individuals with periodontitis are at greater risk for atherosclerosis as well as respiratory infections, we investigated the role of C. pneumoniae in inflammation and periodontal disease. We found that C. pneumoniae was more frequently found in subgingival dental plaque obtained from periodontally diseased sites of the mouth versus healthy sites. The known periodontal pathogens, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, were also found in the plaque.  In addition, C. pneumoniae could efficiently invade human gingival epithelial cells (GECs) in vitro, causing translocation of NF-κB to the nucleus along with increased secretion of mature IL-1β cytokine. Supernatants collected from C. pneumoniae-infected GECs showed increased activation of caspase-1 protein, which was significantly reduced when nlrp3 gene expression was silenced using shRNA lentiviral vectors. Our results demonstrate that C. pneumoniae was found in higher levels in periodontitis patients compared to control patients. Additionally, C. pneumoniae could infect GECs, leading to inflammation caused by activation of NF-κB and the NLRP3 inflammasome. We propose that the presence of C. pneumoniae in subgingival dental plaque may contribute to periodontal disease and could be used as a potential risk indicator of periodontal disease.


Role of pheromone recognition systems in creating new species of fission yeast

Taisuke Seike and Chikashi Shimoda

page 209-211 | 10.15698/mic2019.04.675 | Full text | PDF | Abstract

Many species, from mammals to microorganisms, release sex pheromones to attract a potential partner of the opposite sex. The combination of a pheromone and its corresponding receptor determines the species-specific ability of males and females to recognize each other, and therefore causes reproductive isolation. This barrier, which has arisen to restrict gene flow between mating pairs, might facilitate reproductive isolation leading to incipient speciation, but how do new combinations of pheromone and receptor evolve? Our recent study demonstrated an “asymmetric” pheromone recognition system in the fission yeast Schizosaccharomyces pombe: among the two pheromone/receptor pairs in this yeast, recognition between one pair is stringent, while that between the other pair is rather relaxed. We speculate that the asymmetric properties of these pheromone recognition systems are beneficial for gradual evolution resulting in reproductive isolation in yeasts.

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