Engineering Microbial Biofilms for Improved Productivity of Biochemicals Important in Restoration of Degraded Ecosystems

Biofilms are being engineered in-vitro to produce numerous commodities like biofertilizers, pharmaceuticals, biofuels and electricity, the efficacies of which rely on the biochemicals secreted by the biofilms i.e. extracellular polymeric substances (EPS). It has been shown that once EPS-biochemicals of developed biofilms are applied to an ecosystem, they can restore degraded complex ecosystem networks for improved ecosystem functioning and sustainability. Identification of the EPS biochemicals and understanding their contributions to the network interactions in particular, are at initial stage. In the present study, using Aspergillus niger, Nostoc sp., and gram (-) Stenotrophomonas maltophilia & gram (+) Bacillus subtilis as test fungal (F), cyanobacterial (C), and bacterial (B) counterparts, respectively we analyzed morphology and biochemical parameters of fungal-bacterial (FBBs), fungal-cyanobacterial (FCBs), cyanobacterial-bacterial (CBBs), and fungal-cyanobacterial-bacterial biofilms (FCBBs). Results revealed that the FCBBs produced the highest concentrations of lipids, proteins, and polysaccharides whereas FBBs generated the highest diversity of biochemicals. Bacterial type (i.e. gram + or -) and microbial composition in the biofilm affected the biochemical production. Ecologically and industrially important diverse biochemicals which are used individually as medicines, bioremediating agents and industrial chemicals in human society with certain adverse and beneficial effects were detected in the biofilm-EPS. However, in the nature, simultaneous action of those diverse biochemicals applied as biofertilizers has already shown a huge potential to restore the entire agroecosystems degraded due to farmers’ detrimental practices. This striking difference in utilization of the biochemicals and their enhanced effect when they act simultaneously needs further investigations for their better applications.

Carbon Sequestration in Tropical Forest Stands: Its Control by Plant, Soil and Climatic Factors

This study investigated the relationships amongst floristic, soil and climatic parameters and their control on carbon sequestration (CS) in two selected forest stands of Sri Lanka. Representative sampling sites were selected from the dry zone (Sigiriya forest sanctuary) and the wet zone (Udawattakele forest reserve) of Sri Lanka. Litter and soil samples were collected from each sampling site randomly in monthly intervals to cover an annual cycle. Plant biomass carbon stocks were calculated using standard biomass equations. Soil carbon stocks were determined by chemical oxidation and loss on ignition (LOI) methods. Principle Factor Analysis and multiple regression were used to quantify the relationships among the plants, soil and climatic variables. Plant biomass carbon stocks of the forests were governed by labile and stable C fractions, soil moisture, and plant diversity. The soil fulvic fraction acts as a focal point of interacting the variables such as soil N, free litter fraction (FLF) and humic fraction. During dry period in the dry zone forest, CS was governed by maximum relative humidity through an atmosphere-floor litter-soil continuum. Air temperature and FLF play a vital role in determining soil N. In addition, MacIntosh distance (U) diversity index showed a significant positive relationship with soil N. The dry zone forests are seen to be more climatic sensitive and vulnerable than the wet zone forests in Sri Lanka due to influence of more climatic parameters that govern the soil organic carbon fractions.