Background Gut microbes play a crucial role in the maintenance of human health. Components in the diet of the host affect their metabolism and diversity. Here, we investigated the influences of three commonly used non-caloric artificial sweeteners-aspartame, acesulfame K and sucralose-on the growth and metabolism of an omnipresent gut microbe Escherichia c oli K-12. Methods : Growth of E. coli in the presence of aspartame, acesulfame K and sucralose in media was assessed and the influences of these artificial sweeteners on metabolism were investigated by relative expression analysis of genes encoding the rate limiting steps of important metabolic pathways as well as their global metabolomic profiles. Results: As a whole, E. coli growth was inhibited by aspartame and induced by acesulfame potassium, while the effect of sucralose on growth was less prominent. Although the expressions of multiple key enzymes that regulate important metabolic pathways were significantly altered by all three sweeteners, acesulfame K caused the most notable changes in this regard. In multivariate analysis with the metabolite profiles, the sucralose-treated cells clustered the closest to the untreated cells, while the acesulfame potassium treated cells were the most distant. These sweeteners affect multiple metabolic pathways in E. coli , which include propanoate, phosphonate, phosphinate and fatty acid metabolism, pentose phosphate pathway, and biosynthesis of several amino acids including lysine and the aromatic amino acids. Similar to the gene expression pattern, acesulfame potassium treated E. coli showed the largest deviation in their metabolite profiles compared to the untreated cells.

Aquatic plants are generally considered as breeding grounds for mosquitoes and other harmful vectors of diseases. However, in recent years, some research has been carried out to test their significance as sources of antimicrobial lead molecules. The aim of this research was to study the phytochemical composition of local aquatic plant species and test their antimicrobial effect against selected bacterial strains. Three different aquatic plant samples were collected from a large water body near Dhaka. Ethanol and ethyl acetate extracts of the plant species: Eichhornia crassipes, Pistia stratiotes, and Spirodela polyrrhiza were tested against Staphylococcus aureus, Salmonella typhi, and Lactobacillus spp. Out of the eight different extracts, only the ethyl acetate extracts prepared from Eichhornia crassipes showed significant anti-microbial activity against Staphylococcus aureus and Salmonella typhi. In disk diffusion tests, zone of inhibitions of ethyl acetate extracts of Eichhornia crassipes leaves and stems were 8.00 ± 0.5 mm and 7.83 ± .29 mm respectively. In well diffusion tests, zone of inhibitions of ethyl acetate extracts of Eichhornia crassipes leaves and stems were 18.00 mm and 20.00 mm respectively. Zones of inhibition of ethyl acetate extracts of Eichhornia crassipes stems against Staphylococcus aureus were 7.67 ± 0.29 mm and 12.00 mm respectively in disk and well diffusion tests. Zone of inhibition of ethyl acetate extracts of Spirodela polyrrhiza was 8.17 ± 0.29 mm against Staphylococcus aureus in disk diffusion tests. No extracts showed any antimicrobial potential against Lactobacillus. Phytochemical composition analysis showed the presence of alkaloids, flavonoids, steroids, phenolics, tannins, glycosides, and cardiac glycosides in the different ethanol and ethyl acetate extracts. Tannins were absent in all extracts and saponins were absent in all ethyl acetate extracts. Bangladesh J Microbiol, Volume 35 Number 1 June 2018, pp 7-11

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Costus speciosus (J. Koenig) Sm., commonly known as crepe ginger, is primarily used as an ornamental plant worldwide. The aim of this research was to study the phytoconstituents of locally collected C. speciosus plant samples and test their antimicrobial effect against selected bacterial strains. Phytochemical analysis showed the presence of alkaloids, flavonoids, steroids, phenolic compounds, tannins, glycosides, and cardiac glycosides in the extracts. The extracts displayed variable degrees of antibacterial activity against the microorganisms in a bioautography experiment based on thin-layer chromatography. All the extracts showed activity against S. aureus, and none showed any activity against P. aeuroginosa. The ethanol and ethyl acetate extracts from the plant leaf and stem showed efficacy against S. typhi and B. subtilis, while the ethyl acetate extracts prevented the growth of S. pneumoniae. Only the ethanol extract from plant leaves had a negligible effect on K. pneumoniae. Bangladesh J Microbiol, Volume 39, Number 2, December 2022, pp 46-52