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Concept: Bacteriology



Clonal microbial populations often harbor rare phenotypic variants that are typically hidden within the majority of the remaining cells, but are crucial for the population’s resilience to external perturbations. Persister and viable but non-culturable (VBNC) cells are two important clonal bacterial subpopulations that can survive antibiotic treatment. Both persister and VBNC cells pose a serious threat to human health. However, unlike persister cells, which quickly resume growth following drug removal, VBNC cells can remain non-growing for prolonged periods of time, thus eluding detection via traditional microbiological assays. Therefore, understanding the molecular mechanisms underlying the formation of VBNC cells requires the characterization of the clonal population with single-cell resolution. A combination of microfluidics, time-lapse microscopy, and fluorescent reporter strains offers the perfect platform for investigating individual cells while manipulating their environment.

Concepts: Archaea, Bacteria, Biology, Microbiology, Antibiotic, Microorganism, Bacteriology, Viable but nonculturable


Finding bacterial cellular targets for developing novel antibiotics has become a major challenge in fighting resistant pathogenic bacteria. We present a novel compound, Relacin, designed to inhibit (p)ppGpp production by the ubiquitous bacterial enzyme RelA that triggers the Stringent Response. Relacin inhibits RelA in vitro and reduces (p)ppGpp production in vivo. Moreover, Relacin affects entry into stationary phase in Gram positive bacteria, leading to a dramatic reduction in cell viability. When Relacin is added to sporulating Bacillus subtilis cells, it strongly perturbs spore formation regardless of the time of addition. Spore formation is also impeded in the pathogenic bacterium Bacillus anthracis that causes the acute anthrax disease. Finally, the formation of multicellular biofilms is markedly disrupted by Relacin. Thus, we establish that Relacin, a novel ppGpp analogue, interferes with bacterial long term survival strategies, placing it as an attractive new antibacterial agent.

Concepts: Bacteria, Microbiology, Pathogen, Bacillus, Antibiotic, Pathogenic bacteria, Anthrax, Bacteriology


Glycerol monolaurate (GML) is an antimicrobial agent that has potent activity against gram-positive bacteria. This study examines GML antibacterial activity in comparison to lauric acid, in broth cultures compared to biofilm cultures, and against a wide range of gram-positive, gram-negative, and non-gram staining bacteria.

Concepts: Bacteria, Microbiology, Staining, Gram-negative bacteria, Tea tree oil, Gram staining, Gram-positive bacteria, Bacteriology


In this study, scaling, polishing and daily tooth brushing were performed in 20 beagle dogs, and the number of oral bacteria was determined using a bacterial counter. The dogs were randomized into the scaling (S), scaling + polishing (SP), scaling + tooth daily brushing (SB) and scaling + polishing + tooth daily brushing (SPB) groups. Samples were collected from the buccal surface of the maxillary fourth premolars of the dogs immediately after scaling and every week thereafter from weeks 1 to 8. Throughout the study, the number of bacteria was significantly lower in the SB and SPB groups compared with the S group. The findings suggest that daily tooth brushing inhibited oral bacterial growth in the dogs.

Concepts: Bacteria, Evolution, Microbiology, Beagle, Bacterial cell structure, Bacteriology


Psychobiotics were previously defined as live bacteria (probiotics) which, when ingested, confer mental health benefits through interactions with commensal gut bacteria. We expand this definition to encompass prebiotics, which enhance the growth of beneficial gut bacteria. We review probiotic and prebiotic effects on emotional, cognitive, systemic, and neural variables relevant to health and disease. We discuss gut-brain signalling mechanisms enabling psychobiotic effects, such as metabolite production. Overall, knowledge of how the microbiome responds to exogenous influence remains limited. We tabulate several important research questions and issues, exploration of which will generate both mechanistic insights and facilitate future psychobiotic development. We suggest the definition of psychobiotics be expanded beyond probiotics and prebiotics to include other means of influencing the microbiome.

Concepts: Psychology, Gut flora, Digestive system, Escherichia coli, Probiotic, Lactobacillus, Bacteriology, Prebiotic


OBJECTIVE:To quantify microbial contamination of human milk purchased via the Internet as an indicator of disease risk to recipient infants.METHODS:Cross-sectional sample of human milk purchased via a popular US milk-sharing Web site (2012). Individuals advertising milk were contacted to arrange purchase, and milk was shipped to a rented mailbox in Ohio. The Internet milk samples (n = 101) were compared with unpasteurized samples of milk donated to a milk bank (n = 20).RESULTS:Most (74%) Internet milk samples were colonized with Gram-negative bacteria or had >10(4) colony-forming units/mL total aerobic count. They exhibited higher mean total aerobic, total Gram-negative, coliform, and Staphylococcus sp counts than milk bank samples. Growth of most species was positively associated with days in transit (total aerobic count [log10 colony-forming units/mL] β = 0.71 [95% confidence interval: 0.38-1.05]), and negatively associated with number of months since the milk was expressed (β = -0.36 [95% confidence interval: -0.55 to -0.16]), per simple linear regression. No samples were HIV type 1 RNA-positive; 21% of Internet samples were cytomegalovirus DNA-positive.CONCLUSIONS:Human milk purchased via the Internet exhibited high overall bacterial growth and frequent contamination with pathogenic bacteria, reflecting poor collection, storage, or shipping practices. Infants consuming this milk are at risk for negative outcomes, particularly if born preterm or are medically compromised. Increased use of lactation support services may begin to address the milk supply gap for women who want to feed their child human milk but cannot meet his or her needs.

Concepts: Immune system, Bacteria, Microbiology, Escherichia coli, Milk, Breast milk, Chloramphenicol, Bacteriology


Abstract A new gut bacterial adhesion model has been developed. For this, a continuous-flow bioreactor packed with bacteria-coated beads was designed to simulate the gut lining and other features. In vitro model efficacy shows successful bacterial cell gut adhesions: bacterial adhesion was higher with mucin-alginate compared to controls. In feasibility study, adhesion of Lactobacillus fermentum NCIMB 5221 and Lactobacillus reuteri NCIMB 701359 was investigated for their metabolic activities for bile salt. Bile salt hydrolase (BSH)-active Lactobacillus reuteri exerted higher activity than non-BSH-active L. fermentum. This model has potential use in gut health, probiotic, bacterial cell gut adhesion and other delivery applications.

Concepts: Bacteria, Gut flora, Microbiology, Probiotic, Lactobacillus, Lactobacillaceae, Bacteriology, Lactobacillus reuteri


When cultures of Serratia marcescens, an enterobacteria isolated from the microflora associated with banana plantations incubated at 27°C in a yeast-calcium carbonate-dextrose solid medium (10 g of yeast extract, 20 g dextrose, 15 g bacteriological agar, 20 g calcium carbonate and 1000 mL distilled water) were extracted with chloroform and purified by column chromatography, we obtained a new colourless bacterial metabolite which according to spectroscopic data proved to be serratin.

Concepts: Oxygen, Gut flora, Microbiology, Ethanol, Enterobacteriaceae, Bacteriology, Serratia marcescens, Serratia


ETHNOPHARMACOLOGICAL RELEVANCE: Cyathocline purpurea (D. Don.) O. Ktze. (Asteraceae) is a rare existence Indian medicinal plant and traditionally has antimicrobial property. AIM OF THE STUDY: The aim of the present study was to identify chemical composition of the essential oil from the roots of Cyathocline purpurea and to screened in vitro antibacterial activity against eight human pathogenic bacteria. MATERIALS AND METHODS: The essential oil of roots was analyzed by using GC-FID and GC-MS. The antibacterial activity of oil was tested against four Gram-positive and four Gram-negative bacteria and antibacterial activity was determined by the tube dilution method. RESULTS: The main constituents of the oil were thymohydroquinone dimethyl ether (57.4%) and β-selinene (14.0%), among twenty five identified compounds, which represented 90.1% of the total oil. The oil was found active against Gram-positive bacteria with minimal bactericidal concentration (MBC) values in the range of 0.26-0.57mg/mL. CONCLUSIONS: This is the first report on the chemical composition and antibacterial activity of the essential oil of roots of Cyathocline purpurea. The observation of MBC assay suggested that the Gram positive microorganisms were susceptible to essential oil, while oil was found to be resistant against Gram-negative bacteria, and the oil has bactericidal property.

Concepts: Bacteria, Microbiology, Staining, Pathogenic bacteria, Gram-negative bacteria, Gram staining, Gram-positive bacteria, Bacteriology