Increasing concentrations of carbon dioxide (CO₂), one of the important greenhouse gases, due to combustion of fossil fuels, particularly burning coal, have become the major cause for global warming. As a consequence, many research programs on CO₂ management (capture, storage, and sequestration) are being highlighted. Biological sequestration of CO₂ by algae is gaining importance, as it makes use of the photosynthetic capability of these aquatic species to efficiently capture CO₂ emitted from various industries and converting it into algal biomass as well as a wide range of metabolites such as polysaccharides, amino acids, fatty acids, pigments, and vitamins. In addition, their ability to thrive in rugged conditions such as seawater, contaminated lakes, and even in certain industrial wastewaters containing high organic and inorganic nutrients loads, has attracted the attention of researchers to integrate carbon capture and wastewater treatment. Algae offer a simple solution to tertiary treatments due to their nutrient removal efficiency, particularly inorganic nitrogen and phosphorus uptake. The algal–bacterial energy nexus is an important strategy capable of removing pollutants from wastewater in a synergistic manner. This review article highlights the mechanism involved in biological fixation of CO₂ by microalgae, their cultivation systems, factors influencing algal cultivation in wastewater and CO₂ uptake, the effect of co-cultivation of algae and bacteria in wastewater treatment systems, and challenges and opportunities.

Salinity is one of the major factors contributing to the loss of crop productivity and thereby impacting livelihood of people in more than 100 countries of the world and the area of land affected by salinity is increasing day by day. This will worsen due to various factors such as drought that might result in high soil salinity. Use of plant growth promoting rhizobacteria is one of the promising eco-friendly strategies for salinity stress management as part of sustainable agricultural practices. However, it requires selecting rhizobacteria with good survivability and adaptation to salt stress. In this study we report aggregation of Methylobacterium oryzae CBMB20 cells grown in media containing high C/N ratio (30:1) than in media containing low C/N ratio (7:1). Aggregated Methylobacterium oryzae CBMB20 cells exhibited enhanced tolerance to UV irradiation, heat, desiccation, different temperature regimes, oxidative stress, starvation and supported higher population in media. Poly-β-hydroxybutyrate accumulation, exopolysaccharide production, proline accumulation and biofilm formation were good at 100 mM salt concentration with good microbial cell hydrophobicity at both 50 and 100 mM than other concentrations. Both the aggregated and non-aggregated cells grown under 0–200 mM salt concentrations produced IAA even at 200 mM salt concentration with a peak at 100 mM concentration with aggregated cells producing significantly higher quantities. ACC deaminase activity was observed in all NaCl concentrations studied with gradual and drastic reduction in aggregated and non-aggregated cells over increased salt concentrations.

To investigate variability in colony morphology and antibiotic susceptibility in populations of Pseudomonas aeruginosa from sputa of patients with bronchiectasis without cystic fibrosis (CF) compared with P. aeruginosa isolated from patients with CF, and from other infections as controls. P. aeruginosa was cultured from 31 patients with non-CF bronchiectasis, 24 with CF, 7 ventilated patients and 9 skin swabs. Four colonies of each morphotype of P. aeruginosa were tested for susceptibility to 12 antibiotics by disc diffusion. The variability in susceptibility between the isolates in each patient’s population of P. aeruginosa was investigated. The classic morphotype of P. aeruginosa was cultured from control samples with an average variation in zone size of 2 mm (range 0–4 mm) for the four colonies tested. Non-CF bronchiectasis sputa contained 1–3 colonial morphotypes of P. aeruginosa; the average difference between the largest and smallest zone sizes found in all examples of the morphotypes present in each sample varied from 3 mm (1–9 mm) for colistin to 8 mm (0–24 mm) for piperacillin/tazobactam. CF sputa contained 2–6 morphotypes of P. aeruginosa with a wider variation of susceptibility. There was variation between bacteria of the same morphotype from non-CF bronchiectasis and CF sputa. Phenotypic variation in colonial form and antibiotic susceptibility is not unique to chronic infection in CF but is also found in non-CF bronchiectasis. This questions the use of current susceptibility testing methods for the complex populations of bacteria found in chronic lung infection.

Among the various bacterial isolates, the strain MSF 46 isolated from thorn forest soil samples, Tamil Nadu, India, was screened and characterized for its proteolytic activity. While the 16S rRNA sequencing and biochemical characterization revealed that the strain closely resembles Methylobacterium sp., methylotrophy of the strain was confirmed by the sequence homology of mxaF gene with other relative Methylobacterium sp. The alkaline protease was purified to homogeneity using DEAE cellulose ion exchange chromatography, with a 5.2-fold increase in specific activity and 34% recovery. The apparent molecular weight of the enzyme was determined as 40kDa by SDS–PAGE study. The pH and temperature optima were 9.0 and 50°C respectively with maximum protease activity of 1164U/ml. Protease of MSF 46 was active in a broad pH range 7.0–11.0 with a maximum at pH 8.5 and exhibited thermostability at 50°C. The enzyme activity was inhibited by PMSF but showed stability with Tween 20, Triton X-100 and hydrogen peroxide. Nearly 30% reduction in enzyme activity was observed in the presence of EDTA and DTT. The enzyme was effective in hydrolyzing gelatin, skimmed milk and blood clots and exhibited the potency for dehairing of goat skin and removing blood stain from cotton fabric. Significant morphological changes were observed under scanning electron microscope between cells grown in normal and casein amended medium. This first detailed report on the production of alkaline protease by a PPFM strain appears promising toward development of protocols for mass production, study of the molecular mechanism and other applications