Rathinam Arthur James

The Salina Cruz and Puerto Ángel beach areas in the Gulf of Tehuantepec, Mexican Pacific coast represent an important economic sector of the region. In this study, the mineralogy and geochemistry of bulk sediments, and geochronology of 400 detrital zircons recovered from the beach sediments were analysed to investigate their origin. The sediments are abundant in quartz, feldspar, ilmenite, cordierite, aragonite and anorthite. The chemical index of weathering revealed a moderate to intense weathering in the source area. The chondrite normalized REE patterns of bulk sediments are similar to the found in the Upper Continental Crust, suggesting the derivation of sediments from felsic igneous rocks. The REE patterns of zircons and the trace elemental ratios reveal a continental crust origin. Zircon U–Pb ages in the Salina Cruz beach were represented by Proterozoic (~545.1–1314.1 Ma; n = 170) and Cenozoic (~0.01–66 Ma; n = 20). The Puerto Ángel beach was abundant in Proterozoic zircon grains (~600.9–1171.4 Ma; n = 109) and followed by Mesozoic grains (~73.78–246.9 Ma; n = 40). The comparison of zircon U–Pb ages of this study with probable source rocks reveals that the Oaxaquia Terrane and Chiapas Massif Complex were the major contributors of Proterozoic zircons to the coastal areas. Similarly, the results indicate that the Cenozoic zircons were contributed by the Chiapas Massif Complex, coastal batholith and Cuicateco Terrane. The Mesozoic zircons are very few, derived from the nearby Xolapa Complex and the Chuacús Terrane.

In this study, we report Scanning Electron Microscopy (SEM) images of quartz grains in the Acapulco beach, Mexican Pacific. The morphology of quartz grains is angular, sub-angular, sub-rounded, rounded, and well-rounded. The variations in the morphology of quartz grains are indicating both nearby and distance sources. The rounded and well-rounded grains support for a long transport distance and a distal source. Microtextures of mechanical and chemical origins are identified in quartz grains. The mechanical features include, bulbous edges (ble), elongated depression (ed), parallel striations, crater, meandering ridges (mr), arcuate steps, conchoidal fractures (cf), v-shaped marks (v-s), and broken grain. These mechanical features indicate the combination of fluvial, aeolian, and subaqueous environments. The conchoidal fractures are characteristic of crystalline rocks. Arcuate steps and meandering ridges are indicating a high wave energy. The striations on grain surfaces are due to collision between two grains, probably during an aeolian transport. The chemical features include adhered particles (ap), solution pit (sp), silica globule, crystal overgrowth (crg), precipitation, and trapped diatoms. The solution pits and precipitation are indicating the diagenetic processes in a silica saturated coastal environment. A few grains are associated with both mechanical and chemical features, suggesting a dual environment, probably littoral and marine. Trapped diatoms identified in quartz grains are Cocconeis guttata and coccolith.

Human pathogenic diseases received much attention recently due to their uncontrolled spread of antimicrobial resistance (AMR) which causes several threads every year. Effective alternate antimicrobials are urgently required to combat those disease causing infectious microbes. Halophilic actinobacteria revealed huge potentials and unexplored cultivable/non-cultivable actinobacterial species producing enormous antimicrobials have been proved in several genomics approaches. Potential gene clusters, PKS and NRPKS from Nocardia, Salinospora, Rhodococcus, and Streptomyces have wide range coding genes of secondary metabolites. Biosynthetic pathways identification via various approaches like genome mining, In silico, OSMAC (one strain many compound) analysis provides better identification of knowing the active metabolites using several databases like AMP, APD and CRAMPR, etc. Genome constellations of actinobacteria particularly the prediction of BGCs (Biosynthetic Gene Clusters) to mine the bioactive molecules such as pigments, biosurfactants and few enzymes have been reported for antimicrobial activity. Saltpan, saltlake, lagoon and haloalkali environment exploring potential actinobacterial strains Micromonospora, Kocuria, Pseudonocardia, and Nocardiopsis revealed several acids and ester derivatives with antimicrobial potential. Marine sediments and marine macro organisms have been found as significant population holders of potential actinobacterial strains. Deadly infectious diseases (IDs) including tuberculosis, ventilator-associated pneumonia and Candidiasis, have been targeted by halo-actinobacterial metabolites with promising results. Methicillin resistant Staphylococus aureus and virus like Encephalitic alphaviruses were potentially targeted by halophilic actinobacterial metabolites by the compound Homoseongomycin from sponge associated antinobacterium. In this review, we discuss the potential antimicrobial properties of various biomolecules extracted from the unexplored halophilic actinobacterial strains specifically against human infectious pathogens along with prospective genomic constellations.

Alternative treatment strategies for urinary tract infections (UTIs) are becoming more necessary due to increasing drug resistance patterns in uropathogens. Nanoparticle-based therapeutics is emerging as a way to treat UTIs. In the present study, using Turbinaria ornata extract, silver nanoparticles (AgNPs) were synthesized, characterized, and their anti-uropathogenic activity was evaluated. The stability and formation of synthesized To-AgNPs were confirmed by UV-visible spectroscopy, FTIR, XRD, SEM, and DLS. An FTIR spectrum confirmed the presence of seaweed functional groups in To-AgNPs, a XRD analysis confirmed their crystalline nature, and SEM imaging confirmed their spherical nature with an average size of 73.98 nm with diameters ranging from 64.67 to 81.28 nm. This was confirmed by TEM results. DLS determined that the cumulant hydrodynamic diameter of To-AgNPs was 128.3 nm with a PdI of 0.313 and the zeta potential value were found to be –63.3 mV which indicates the To-AgNPs are negatively charged and more stable. DPPH assays were used to assess the antioxidant activity of biosynthesized To-AgNPs, while an agar well diffusion method was used to test the antibacterial activity against uropathogens, including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, and Klebsiella pneumoniae. The To-AgNPs showed the highest susceptibility to S. aureus (15.75 ± 0.35 mm) and E. coli (15 ± 0.7 mm) with MIC values of 0.0625 and 0.125 mg/ml, respectively in macro broth dilution method and observed considerable membrane damage under CLSM and SEM. To-AgNPs displayed stronger antioxidant and antimicrobial activity, suggesting they may be developed as a new class of antimicrobial agents for treating UTIs.

This study aimed to characterize the sedimentary facies and understand the morphodynamics of the study area, and their results were correlated with various analytical methods. Different analyses such as depositional environmental, statistical, shoreline change, and grain size illustrated the temporal and spatial distribution of sediments. It has previously been claimed that current research locations are locii to fluvial landforms and are affected by fluvial processes. However, there are currently no rivers in the study region. This study was done to better understand the presence of fluvial landforms and to evaluate the previous findings. The dynamic behavior of the coast was revealed through shoreline analysis, which was done using satellite images from various years. Oceanographic parameters and longshore sediment transport play a vital role in geomorphological changes in coastal zones. According to the grain size analysis results, mean values showed that the deposits predominantlyare medium grained. The outcome discussed the spatiotemporal variations in geomorphology, sedimentation, and the function of coastal and fluvial processes on the beach of an island and a sand spit. Also highlighted was the role that wave action, fluvial currents, and tidal currents had in the long-term evolution of coastal geomorphological features such as spits, beaches, open coasts, and islands. The standard deviation signifies that the sediments are very well sorted to poorly sorted. Skewness ranges from fine skewed to strongly fine skewed and the kurtosis values show that the sediments are predominately very platykurtic which implies a low-energy environment of deposition. Four sedimentary facies (Facies A, B, C, D) have been found and facies A, B, and C may be wave-influenced deposits, but facies D may be formed by fluvial processes and contain medium to sand-sized particles. The direction of the tip area is also pointing to the south and this result concluded that the tip area is continuously growing. Thus, the results of this study revealed that sediment transport and coastal geomorphology evolution may be governed by two main processes such as the present ocean hydrodynamics and paleo fluvial processes of the study regions.