In situ cell division and mortality rates of SAR11, SAR86, Bacteroidetes, and Aurantivirga during phytoplankton blooms reveal differences in population controls

Net growth of microbial populations, i.e., changes in abundances over time, can be studied using 16S rRNA fluorescence in situ hybridization (FISH). However, this approach does not differentiate between mortality and cell division rates. We used FISH-based image cytometry in combination with dilution culture experiments to study net growth, cell division, and mortality rates of four bacterial taxa over two distinct phytoplankton blooms: the oligotrophs SAR11 and SAR86, the copiotrophic phylum Bacteroidetes, and its genus Aurantivirga. Cell volumes, ribosome content, and frequency of dividing cells (FDC) co-varied over time. Among the three, FDC was the most suitable predictor to calculate the cell division rates for the selected taxa. The FDC-derived cell division rates for SAR86 of up to 0.8 d-1 and Aurantivirga of up to 1.9 d-1 differed, as expected for oligotrophs and copiotrophs. Surprisingly, SAR11 also reached high cell division rates of up to 1.9 d-1, even before the onset of phytoplankton blooms. For all four taxonomic groups, the abundance-derived net growth (-0.6 to 0.5 d-1) was about an order of magnitude lower than the cell division rates. Consequently, mortality rates were comparably high to cell division rates, indicating that about 90% of bacterial production is recycled without apparent time lag within one day. Our study shows that determining taxon-specific cell division rates complements omics-based tools and provides unprecedented clues on individual bacterial growth strategies including bottom-up and top-down controls

Isolation and Taxonomic Characterization of Novel Haloarchaeal Isolates From Indian Solar Saltern: A Brief Review on Distribution of Bacteriorhodopsins and V-Type ATPases in Haloarchaea

Haloarchaea inhabit high salinity environments worldwide. They are a potentially rich source of crucial biomolecules like carotenoids and industrially useful proteins. However, diversity in haloarchaea present in Indian high salinity environments is poorly studied. In the present study, we isolated 12 haloarchaeal strains from hypersaline Kottakuppam, Tamil Nadu solar saltern in India. 16S rRNA based taxonomic characterization of these isolates suggested that nine of them are novel strains that belong to genera Haloarcula, Halomicrobium, and Haloferax. Transmission electron microscopy suggests the polymorphic nature of these haloarchaeal isolates. Most of the haloarchaeal species are known to be high producers of carotenoids. We were able to isolate carotenoids from all these 12 isolates. The UV-Vis spectroscopy-based analysis suggests that bacterioruberin and lycopene are the major carotenoids produced by these isolates. Based on the visual inspection of the purified carotenoids, the isolates were classified into two broad categories i.e., yellow and orange, attributed to the differences in the ratio of bacterioruberin and lycopene as confirmed by the UV-Vis spectral analysis. Using a PCR-based screening assay, we were able to detect the presence of the bacteriorhodopsin gene (bop) in 11 isolates. We performed whole-genome sequencing for three bop positive and one bop negative haloarchaeal isolates. Whole-genome sequencing, followed by pan-genome analysis identified multiple unique genes involved in various biological functions. We also successfully cloned, expressed, and purified functional recombinant bacteriorhodopsin (BR) from one of the isolates using Escherichia coli as an expression host. BR has light-driven proton pumping activity resulting in the proton gradient across the membrane, which is utilized by V-Type ATPases to produce ATP. We analyzed the distribution of bop and other accessory genes involved in functional BR expression and ATP synthesis in all the representative haloarchaeal species. Our bioinformatics-based analysis of all the sequenced members of genus Haloarcula suggests that bop, if present, is usually inserted between the genes coding for B and D subunits of the V-type ATPases operon. This study provides new insights into the genomic variations in haloarchaea and reports expression of new BR variant having good expression in functional form in E. coli

Unraveling the microbial interactions and metabolic potentials in pre- and post-treated sludge from a wastewater treatment plant using metagenomic studies

Sewage waste represents an ecosystem of complex and interactive microbial consortia which proliferate with different kinetics according to their individual genetic as well as metabolic potential. We performed metagenomic shotgun sequencing on Ion-Torrent platform, to explore the microbial community structure, their biological interactions and associated functional capacity of pre-treated/raw sludge (RS) and posttreated/dried sludge (DS) of wastewater treatment plant. Bacterial phylotypes belonging to Epsilonproteobacteria (45.80%) dominated the RS with relatively few Archaea (1.94%) whereas DS has the dominance of beta-(30.23%) and delta- (13.38%) classes of Proteobacteria with relatively greater abundance of Archaea (7.18%). In particular, Epsilonproteobacteria appears as a primary energy source in RS and sulfurreducing bacteria with methanogens seems to be in the potential syntrophic association in DS. These interactions could be ultimately responsible for carrying out aminoacid degradation, aromatic compound degradation and degradation of propionate and butyrate in DS. Our data also reveal the presence of key genes in the sludge microbial community responsible for degradation of polycyclic aromatic hydrocarbons. Potential pathogenic microbes and genes for the virulence factors were found to be relatively abundant in RS which clearly reflect the necessity of treatment of RS. After treatment, potential pathogens load was reduced, indicating the sludge hygienisation in DS. Additionally, the interactions found in this study would reveal the biological and environmental cooperation among microbial communities for domestic wastewater treatment.Department of Biotechnology (DBT), Government of India, UGC, Claude Leon Foundation, South Africa, Council of Scientific and Industrial Research (CSIR), Government of Indiahttp://www.frontiersin.org/Microbiologyam2017Genetic

Unraveling the Microbial Interactions and Metabolic Potentials in Pre- and Post-treated Sludge from a Wastewater Treatment Plant Using Metagenomic Studies

Sewage waste represents an ecosystem of complex and interactive microbial consortia which proliferate with different kinetics according to their individual genetic as well as metabolic potential. We performed metagenomic shotgun sequencing on Ion-Torrent platform, to explore the microbial community structure, their biological interactions and associated functional capacity of pre-treated/raw sludge (RS) and posttreated/dried sludge (DS) of wastewater treatment plant. Bacterial phylotypes belonging to Epsilonproteobacteria (45.80%) dominated the RS with relatively few Archaea (1.94%) whereas DS has the dominance of beta-(30.23%) and delta- (13.38%) classes of Proteobacteria with relatively greater abundance of Archaea (7.18%). In particular, Epsilonproteobacteria appears as a primary energy source in RS and sulfurreducing bacteria with methanogens seems to be in the potential syntrophic association in DS. These interactions could be ultimately responsible for carrying out aminoacid degradation, aromatic compound degradation and degradation of propionate and butyrate in DS. Our data also reveal the presence of key genes in the sludge microbial community responsible for degradation of polycyclic aromatic hydrocarbons. Potential pathogenic microbes and genes for the virulence factors were found to be relatively abundant in RS which clearly reflect the necessity of treatment of RS. After treatment, potential pathogens load was reduced, indicating the sludge hygienisation in DS. Additionally, the interactions found in this study would reveal the biological and environmental cooperation among microbial communities for domestic wastewater treatment.Department of Biotechnology (DBT), Government of India, UGC, Claude Leon Foundation, South Africa, Council of Scientific and Industrial Research (CSIR), Government of Indiahttp://www.frontiersin.org/Microbiologyam2017Genetic

Unraveling the Microbial Interactions and Metabolic Potentials in Pre- and Post-treated Sludge from a Wastewater Treatment Plant Using Metagenomic Studies

Sewage waste represents an ecosystem of complex and interactive microbial consortia which proliferate with different kinetics according to their individual genetic as well as metabolic potential. We performed metagenomic shotgun sequencing on Ion-Torrent platform, to explore the microbial community structure, their biological interactions and associated functional capacity of pre-treated/raw sludge (RS) and post-treated/dried sludge (DS) of wastewater treatment plant. Bacterial phylotypes belonging to Epsilonproteobacteria (∼45.80%) dominated the RS with relatively few Archaea (∼1.94%) whereas DS has the dominance of beta- (30.23%) and delta- (13.38%) classes of Proteobacteria with relatively greater abundance of Archaea (∼7.18%). In particular, Epsilonproteobacteria appears as a primary energy source in RS and sulfur-reducing bacteria with methanogens seems to be in the potential syntrophic association in DS. These interactions could be ultimately responsible for carrying out amino-acid degradation, aromatic compound degradation and degradation of propionate and butyrate in DS. Our data also reveal the presence of key genes in the sludge microbial community responsible for degradation of polycyclic aromatic hydrocarbons. Potential pathogenic microbes and genes for the virulence factors were found to be relatively abundant in RS which clearly reflect the necessity of treatment of RS. After treatment, potential pathogens load was reduced, indicating the sludge hygienisation in DS. Additionally, the interactions found in this study would reveal the biological and environmental cooperation among microbial communities for domestic wastewater treatment

Extracellular polysaccharide production by a novel osmotolerant marine strain of Alteromonas macleodii and its application towards biomineralization of silver.

The present study demonstrates exopolysaccharide production by an osmotolerant marine isolate and also describes further application of the purified polysaccharide for production of colloidal suspension of silver nanoparticles with narrow size distribution. Phylogenetic analysis based on 16S r RNA gene sequencing revealed close affinity of the isolate to Alteromonas macleodii. Unlike earlier reports, where glucose was used as the carbon source, lactose was found to be the most suitable substrate for polysaccharide production. The strain was capable of producing 23.4 gl(-1) exopolysaccharide with a productivity of 7.8 gl(-1) day(-1) when 15% (w/v) lactose was used as carbon source. Furthermore, the purified polysaccharide was able to produce spherical shaped silver nanoparticles of around 70 nm size as characterized by Uv-vis spectroscopy, Dynamic light scattering and Transmission electron microscopy. These observations suggested possible commercial potential of the isolated strain for production of a polysaccharide which has the capability of synthesizing biocompatible metal nanoparticle

EPS elaboration and biomass production at variable concentrations of lactose at 72<i>Alteromonas macleodii</i> PA2.

<p>EPS elaboration and biomass production at variable concentrations of lactose at 72<i>Alteromonas macleodii</i> PA2.</p

FT-IR analysis to decipher mechanism of nanoparticle biosynthesis.

<p>(A) FT-IR spectra of the polysaccharide produced by <i>A.macleodii</i> PA2 (B) FT-IR spectra of the AgNP produced and stabilized by the polysaccharide.</p

Fermentative production of exopolysaccharide.

<p>(A) Effect of different carbon sources on exopolysaccharide elaboration and biomass production by <i>Alteromonas macleodii</i> PA2. (B) Time course of exopolysaccharide production at different concentrations of lactose by <i>Alteromonas macleodii</i> PA2.</p

Taxonomic characterization of the producing microbe.

<p>(A) Phase contrast microphotograph of the strain <i>Alteromonas macleodii</i> PA2. (B) Neighbour-joining tree based on 16S rRNA gene sequences showing the phylogenetic relationship.</p