Browsing by Author "Megahed, Salwa A"

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Anaerobic biodegradation of anthracene by oral Firmicutes isolates from smokers and its potential pathway
(Elsevier Ltd., 2023-04) Wasfi, Reham; Moussa, Hams A; Bakr, Riham O; Abdeltawab, Nourtan F; Megahed, Salwa A
Exposure to polycyclic aromatic hydrocarbons (PAHs) from tobacco smoke has been linked to many negative health effects. Studies on the biodegradation of PAHs by human microbiota and detailed pathways for their anaerobic biodegradation are scarce despite their importance in getting rid of these toxic compounds. In a previous study for our group, we determined the ability of oral bacterial isolates in the anaerobic biodegradation of anthracene as a model of PAHs. Three isolates with the highest anthracene degradation ability were selected for the present study which include Limosilactobacillus fermentum, Veillonella parvula, and Streptococcus anginosus. In this study, we aimed at exploring and elucidating the anthracene anaerobic biodegradation pathways in selected Firmicutes oral isolates. Metabolites throughout the pathway were detected by gas chromatography coupled with mass spectroscopy (GC-MS) using anthracene as sole source of carbon. After incubation for 3 days, anthracene was undetected in the supernatant of L. fermentum and V. parvula, while a residual of 3% of anthracene was detected in presence of S. anginosus. Results revealed that anaerobic biodegradation by L. fermentum and V. parvula started with hydroxylation and dehydrogenation producing 9,10- anthraquinone and ended up with simpler structures such as catechol, while S. anginosus hydroxylation for anthracene resulted in the production of 1,2-anthracenediol and ended up with catechol and phthalic acid. The biodegradation of anthracene by oral bacteria could convert it to other toxic metabolites such as anthraquinone and catechol which were reported to have potential carcinogenic effects. Moreover, fatty acids detected as biodegradation metab- olites could be one of the causes of smokers’ heart-related diseases. Thus, this study explored oral metabolites resulting from smoking under anaerobic conditions towards elucidating the role of oral microbiota in health and disease states.
High Counts and Anthracene Degradation Ability of Streptococcus mutans and Veillonella parvula Isolated From the Oral Cavity of Cigarette Smokers and Non-smokers
(Frontiers, 6/28/2021) Moussa, Hams A; Wasfi, Reham; Abdeltawab, Nourtan F; Megahed, Salwa A
The composition and metabolic functions of oral microbiota are affected by many factors including smoking leading to several health problems. Cigarette smoking is associated with changes in oral microbiota composition and function. However, it is not known if the depletion of certain bacterial genera and species is due to specific toxins in cigarette smoke, or indirectly due to competition for colonization with smoking-enriched bacteria. Therefore, the aim of this study was to determine the effect of cigarette smoking on the microbial prevalence and polycyclic aromatic hydrocarbons (PAHs) biodegradation of selected enriched and depleted oral bacteria from oral microbiota of smokers compared to that in non-smokers. Samples of oral rinse from smokers and non-smokers were collected (n = 23, 12 smokers and 11 non-smokers) and screened for oral bacterial strains of Streptococcus mutans, Lactobacillus spp., and Veillonella spp. Comparing counts, S. mutans, V. tobetsuensis, and V. dispar showed higher counts in smokers compared to non-smokers while the Lactobacillus spp. were higher in non-smokers. Lactobacillus fermentum was prevalent in smokers, representing 91.67% of the total Lactobacillus spp. isolates. The biodegradation potential of anthracene; a representative of PAHs of collected isolates, in single and mixed cultures, was assayed with anthracene as the sole source of carbon using 2,6-dichlorophenol indophenol (2,6-DCPIP) as indicator. S. mutans isolates recovered from smokers showed higher degradation of anthracene compared to those recovered from non-smokers. The anaerobic anthracene biodegradation activity of V. parvula isolates from non-smokers was the highest among all isolates of the three recovered genera from the same subject. The anthracene biodegradation potential of Lactobacillus spp. was variable. Combinations of isolated bacteria in co-cultures showed that Lactobacillus spp. interfered with anthracene biodegradation ability along with the viable counts of S. mutans and Veillonella spp. In conclusion, oral dysbiosis due to cigarette smoking was observed not only due to changes in oral bacterial relative abundance but also extended to bacterial functions Frontiers in Microbiology | www.frontiersin.org 1 June 2021 | Volume 12 | Article 661509 Moussa et al. Anthracene Biodegradation by Oral Bacteria such as anthracene biodegradation tested in this study. Microbe-microbe interactions changed the anthracene biodegradation potential and growth of the microbial mixture compared to their corresponding single isolates, and these changes differ according to the constituting bacteria.
Spatiotemporal Analysis of the Water and Sediment Nile Microbial Community Along an Urban Metropolis
(Springer, 01/08/2021) Eraqi, Walaa A.; ElRakaiby, Marwa T; Megahed, Salwa A; Yousef, Noha H.; Elshahed, Mostafa S.; Yassin, Aymen S
Assessing microbial identity, diversity, and community structure could be a valuable tool for monitoring the impact of xenobiotics and anthropogenic inputs in rivers, especially in urban and industrial settings. Here, we characterize the Nile River microbial communityinwater and sediments insummerandwinteratfivelocations thatspanits natural flow through the Cairo metropolis. 16SrRNAgenedatasetswereanalyzedtoidentifytherole playedbysampletype(sedimentversuswater),season,andlocationin shaping the community, as well as to predict functional potential of the Nile River microbiome. Microbial communities were mostly influenced by sampling type (sediments versus water), while seasonal effects were only observed in water samples. Spatial differences did not represent a significant factor in shaping the community in either summer or winter seasons. Proteobacteria was the most abundant phylum in both water and sediment samples, with the order Betaproteobacteriales being the abundant one. Chloroflexi and Bacteroidetes were also prevalent in sediment samples, while Cyanobacteria and Actinobacteria were abundant in water samples. The linear discriminative analysis effect size (LEfSe) identified the cyanobacterial genus Cyanobium PCC-6307 as the main variable between summer and winter water. Sequences representing human and animal potential pathogens, as well as toxin-producing Cyanobacteria, were identified in low abundance within the Nile microbiome. Functionally predicted metabolic pathways predicted the presence of antibiotic biosynthesis, as well as aerobic xenobiotic degradation pathways in the river microbiome.