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Keywords = bacteria on toys

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12 pages, 3021 KiB  
Article
CdgB Regulates Morphological Differentiation and Toyocamycin Production in Streptomyces diastatochromogenes 1628
by Rui Wang, Zixuan Zhang, Xiaoping Yu, Yang Song and Xuping Shentu
Int. J. Mol. Sci. 2024, 25(7), 3878; https://doi.org/10.3390/ijms25073878 - 30 Mar 2024
Cited by 3 | Viewed by 1563
Abstract
Bis (3′,5′)-cyclic diguanylic acid (c-di-GMP) is a ubiquitous second messenger that controls several metabolic pathways in bacteria. In Streptomyces, c-di-GMP is associated with morphological differentiation, which is related to secondary metabolite production. In this study, we identified and characterized a diguanylate cyclase [...] Read more.
Bis (3′,5′)-cyclic diguanylic acid (c-di-GMP) is a ubiquitous second messenger that controls several metabolic pathways in bacteria. In Streptomyces, c-di-GMP is associated with morphological differentiation, which is related to secondary metabolite production. In this study, we identified and characterized a diguanylate cyclase (DGC), CdgB, from Streptomyces diastatochromogenes 1628, which may be involved in c-di-GMP synthesis, through genetic and biochemical analyses. To further investigate the role of CdgB, the cdgB-deleted mutant strain Δ-cdgB and the cdgB-overexpressing mutant strain O-cdgB were constructed by genetic engineering. A phenotypic analysis revealed that the O-cdgB colonies exhibited reduced mycelium formation, whereas the Δ-cdgB colonies displayed wrinkled surfaces and shriveled mycelia. Notably, O-cdgB demonstrated a significant increase in the toyocamycin (TM) yield by 47.3%, from 253 to 374 mg/L, within 10 days. This increase was accompanied by a 6.7% elevation in the intracellular concentration of c-di-GMP and a higher transcriptional level of the toy cluster within four days. Conversely, Δ-cdgB showed a lower c-di-GMP concentration (reduced by 6.2%) in vivo and a reduced toyocamycin production (decreased by 28.9%, from 253 to 180 mg/L) after 10 days. In addition, S. diastatochromogenes 1628 exhibited a slightly higher inhibitory effect against Fusarium oxysporum f. sp. cucumerinum and Rhizoctonia solani compared to Δ-cdgB, but a lower inhibition rate than that of O-cdgB. The results imply that CdgB provides a foundational function for metabolism and the activation of secondary metabolism in S. diastatochromogenes 1628. Full article
(This article belongs to the Section Molecular Biology)
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9 pages, 1436 KiB  
Article
Toys in the Playrooms of Children’s Hospitals: A Potential Source of Nosocomial Bacterial Infections?
by Viktorija Aleksejeva, Anastasija Dovbenko, Juta Kroiča and Ingus Skadiņš
Children 2021, 8(10), 914; https://doi.org/10.3390/children8100914 - 14 Oct 2021
Cited by 3 | Viewed by 3038
Abstract
Pediatric patients are more susceptible and vulnerable to nosocomial infections, in part because of their nascent and developing immune system and in part due to certain congenital conditions. Consequently, we found limited literature that investigated and reported children’s toys in hospital playrooms as [...] Read more.
Pediatric patients are more susceptible and vulnerable to nosocomial infections, in part because of their nascent and developing immune system and in part due to certain congenital conditions. Consequently, we found limited literature that investigated and reported children’s toys in hospital playrooms as potential reservoirs of pathogenic microbes. Hence, in the present study, we aimed to investigate toys as potential vectors for nosocomial infections in children’s hospitals. Microbiological samples from 120 toys were collected between April 2018 and November 2018. The specimens were cultivated on suitable cultivation agars for 24–72 h at 37 °C and CFU/cm2 (colony forming units) was determined. Antibiotic susceptibility testing was performed using disc diffusion and E-tests. Our results indicate that 84% of samples were contaminated with different microbes. Four distinct genera and thirty-seven species of bacteria were identified. The most frequently isolated pathogen was Sphingomonas paucimobilis (>603 CFU/cm2). Most of the identified microorganisms were members of normal human microbiota. Although Staphylococcus aureus and Acinetobacter baumannii were identified, CFU/cm2 was relatively low and they were found to be sensitive to antibiotics. Additionally, plastic toys showed the highest average CFU/cm2 of 91.9. Our results bolster the need for adoption and strict enforcement of proper disinfection techniques for toys in the hospital playrooms. Full article
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23 pages, 3048 KiB  
Article
Fully Quantum Modeling of Exciton Diffusion in Mesoscale Light Harvesting Systems
by Fulu Zheng, Lipeng Chen, Jianbo Gao and Yang Zhao
Materials 2021, 14(12), 3291; https://doi.org/10.3390/ma14123291 - 14 Jun 2021
Cited by 12 | Viewed by 3742
Abstract
It has long been a challenge to accurately and efficiently simulate exciton–phonon dynamics in mesoscale photosynthetic systems with a fully quantum mechanical treatment due to extensive computational resources required. In this work, we tackle this seemingly intractable problem by combining the Dirac–Frenkel time-dependent [...] Read more.
It has long been a challenge to accurately and efficiently simulate exciton–phonon dynamics in mesoscale photosynthetic systems with a fully quantum mechanical treatment due to extensive computational resources required. In this work, we tackle this seemingly intractable problem by combining the Dirac–Frenkel time-dependent variational method with Davydov trial states and implementing the algorithm in graphic processing units. The phonons are treated on the same footing as the exciton. Tested with toy models, which are nanoarrays of the B850 pigments from the light harvesting 2 complexes of purple bacteria, the methodology is adopted to describe exciton diffusion in huge systems containing more than 1600 molecules. The superradiance enhancement factor extracted from the simulations indicates an exciton delocalization over two to three pigments, in agreement with measurements of fluorescence quantum yield and lifetime in B850 systems. With fractal analysis of the exciton dynamics, it is found that exciton transfer in B850 nanoarrays exhibits a superdiffusion component for about 500 fs. Treating the B850 ring as an aggregate and modeling the inter-ring exciton transfer as incoherent hopping, we also apply the method of classical master equations to estimate exciton diffusion properties in one-dimensional (1D) and two-dimensional (2D) B850 nanoarrays using derived analytical expressions of time-dependent excitation probabilities. For both coherent and incoherent propagation, faster energy transfer is uncovered in 2D nanoarrays than 1D chains, owing to availability of more numerous propagating channels in the 2D arrangement. Full article
(This article belongs to the Special Issue Recent Advances in Photosynthetic Materials)
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12 pages, 216 KiB  
Article
Bacterial Contamination on Household Toys and Association with Water, Sanitation and Hygiene Conditions in Honduras
by Christine E. Stauber, Adam Walters, Anna M. Fabiszewski De Aceituno and Mark D. Sobsey
Int. J. Environ. Res. Public Health 2013, 10(4), 1586-1597; https://doi.org/10.3390/ijerph10041586 - 18 Apr 2013
Cited by 16 | Viewed by 9482
Abstract
There is growing evidence that household water treatment interventions improve microbiological water quality and reduce diarrheal disease risk. Few studies have examined, however, the impact of water treatment interventions on household-level hygiene and sanitation. This study examined the association of four water and [...] Read more.
There is growing evidence that household water treatment interventions improve microbiological water quality and reduce diarrheal disease risk. Few studies have examined, however, the impact of water treatment interventions on household-level hygiene and sanitation. This study examined the association of four water and sanitation conditions (access to latrines, improved sanitation, improved water and the plastic biosand filter) on the levels of total coliforms and E. coli on existing and introduced toys during an on-going randomized controlled trial of the plastic biosand filter (plastic BSF). The following conditions were associated with decreased bacterial contamination on children’s toys: access to a latrine, access to improved sanitation and access to the plastic BSF. Overall, compared to existing toys, introduced toys had significantly lower levels of both E. coli and total coliforms. Results suggest that levels of fecal indicator bacteria contamination on children’s toys may be associated with access to improved water and sanitation conditions in the home. In addition, the fecal indicator bacteria levels on toys probably vary with duration in the household. Additional information on how these toys become contaminated is needed to determine the usefulness of toys as indicators or sentinels of water, sanitation and hygiene conditions, behaviors and risks. Full article
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