Microplastics pollution in the river Karnaphuli: a preliminary study on a tidal confluence river in the southeast coast of Bangladesh.

Bangladesh is a deltaic country in Asia, and its riverine systems ultimately drain into the Bay of Bengal. Plastic is a severe environmental issue for coastal-marine ecosystems due to the indiscriminate usage and discarding of plastic items in the upstream river that eventually find their route into the Bay of Bengal. Microplastics (MPs) are widespread pollutants in almost all environmental compartments, including aquatic environments. This study aimed to quantify and understand the distribution of microplastics in surface water and sediments of the river Karnaphuli, a tidal confluence river adjacent to the Chattogram seaport city of Bangladesh, a highly inhabited and industrial area on the southeast coast of the Bay of Bengal. A manta trawl net (300-µm mesh size) was used to collect surface water samples, while an Ekman dredge was used to collect sediment samples. The concentrations of microplastics in the surface water of the river Karnaphuli during late monsoon, winter, and early summer were recorded to be 120,111.11, 152,222.22, and 164,444.44 items/km2, respectively, while in sediments, those were recorded to be 103.83, 137.50, and 103.67 items/kg, respectively. A higher abundance of microplastics was observed in downstream surface water (228,888.88 items/km2) and sediments (164.17 items/kg). Smaller sizes (0.3 to 0.5 mm) of microplastics were predominant, fibers or threads were the frequent types, and black was the most common color in the river Karnaphuli. The Fourier transform infrared analysis revealed that polyethylene terephthalate (surface water: 22%, sediments: 19%), polyamide (surface water: 15%, sediments: 13%), polyethylene (surface water: 12%, sediments: 18%), polystyrene (surface water: 13%, sediments: 11%), and alkyd resin (surface water: 13%, sediments: 10%) were the most prevalent polymers in the river Karnaphuli. Moreover, there was a moderate positive correlation between MPs abundance in surface water and sediments. Therefore, improved long-term research (in different seasons with horizontal and vertical monitoring) is necessary in order to accurately determine the flux of microplastics from the river Karnaphuli to the Bay of Bengal.

Purification and Functional Characterization of the Effects on Cell Signaling of Mytilectin: A Novel ß-Trefoil Lectin from Marine Mussels.

In the 2010s, a novel lectin family with ß-trefoil folding has been identified in marine mussels from the family Mytilidae (phylum Mollusca). "MytiLec-1," the lectin described in this chapter, was the first member of this family to be isolated and characterized from the Mediterranean mussel Mytilus galloprovincialis, a commercially and ecologically important species, spread in marine coastal areas worldwide. MytiLec-1 bound to the sugar moiety of globotriose (Gb3: Galα1-4Galß1-4Glc), an α-galactoside, leading to apoptosis of Gb3-expressing Burkitt's lymphoma cells. Although the primary structure of MytiLec-1 was quite unusual, its three-dimensional structure was arranged as a ß-trefoil fold, which is the typical architecture of "Ricin B chain (or R)-type" lectins, which are found in a broad range of organisms. To date, MytiLec-1-like lectins have been exclusively found in a few species of the mollusk family Mytilidae (M. galloprovincialis, M. trossulus, M. californianus, and Crenomytilus grayanus) and in the phylum Brachiopoda. Transcriptome data revealed the presence of different structural forms of mytilectin in mussels, which included prototype and chimera-type proteins. The primary sequence of these lectins did not match any previously described known protein family, leading to their assignment to the new "mytilectin family." We here report the method of purification of this lectin and describe its use in cell biology.