Meenakshi Dua

Biotechnology and bioremediation: successes and limitations

Abstract. With advances in biotechnology, bioremediation has become one of the most rapidly developing fields of environmental restoration, utilizing microorganisms to reduce the concentration and toxicity of various chemical pollutants, such as petroleum hydrocarbons, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, phthalate esters, nitroaromatic compounds, industrial solvents, pesticides and metals. A number of bioremediation strategies have been developed to treat contaminated wastes and sites. Selecting the most appropriate strategy to treat a specific site can be guided by considering three basic principles: the amenability of the pollutant to biological transformation to less toxic products (biochemistry), the accessibility of the contaminant to microorganisms (bioavailability) and the opportunity for optimization of biological activity (bioactivity). Recent advances in the molecular genetics of biodegradation and studies on enzyme-tailoring and DNA-shuffling are discussed in this paper.

Group B Streptococcus: global incidence and vaccine development.

An ongoing public health challenge is to develop vaccines that are effective against infectious diseases that have global relevance. Vaccines against serotypes of group B Streptococcus (GBS) that are prevalent in the United States and Europe are not optimally efficacious against serotypes common to other parts of the world. New technologies and innovative approaches are being used to identify GBS antigens that overcome serotype-specificity and that could form the basis of a globally effective vaccine against this opportunistic pathogen. This Review highlights efforts towards this goal and describes a template that can be followed to develop vaccines against other bacterial pathogens.

The root endophyte fungus Piriformospora indica leads to early flowering, higher biomass and altered secondary metabolites of the medicinal plant, Coleus forskohlii

This study was undertaken to investigate the influence of plant probiotic fungus Piriformospora indica on the medicinal plant C. forskohlii. Interaction of the C. forskohlii with the root endophyte P. indica under field conditions, results in an overall increase in aerial biomass, chlorophyll contents and phosphorus acquisition. The fungus also promoted inflorescence development, consequently the amount of p-cymene in the inflorescence increased. Growth of the root thickness was reduced in P. indica treated plants as they became fibrous, but developed more lateral roots. Because of the smaller root biomass, the content of forskolin was decreased. The symbiotic interaction of C. forskohlii with P. indica under field conditions promoted biomass production of the aerial parts of the plant including flower development. The plant aerial parts are important source of metabolites for medicinal application. Therefore we suggest that the use of the root endophyte fungus P. indica in sustainable agriculture will enhance the medicinally important chemical production.

Degradation of alpha, beta, gamma and delta-hexachlorocyclohexanes by Sphingomonas paucimobilis

Sphingomonas paucimobilis degrades aerobically α, β, γ and δ-hexachlorocyclohexane. With α-HCH, complete degradation occurred after 3 days but with β and γ, and with δ-HCH, 98 and 56 % degradation occurred after 12 and 8 days of incubation, respectively. Pentachlorocyclohexene was formed as the primary metabolite during the degradation of all the HCH isomers.

Piriformospora indica rescues growth diminution of rice seedlings during high salt stress

Piriformospora indica association has been reported to increase biotic as well as abiotic stress tolerance of its host plants. We analyzed the beneficial effect of P. indica association on rice seedlings during high salt stress conditions (200 and 300 mM NaCl). The growth parameters of rice seedlings such as root and shoot lengths or fresh and dry weights were found to be enhanced in P. indica-inoculated rice seedlings as compared with non-inoculated control seedlings, irrespective of whether they are exposed to salt stress or not. However, salt-stressed seedlings performed much better in the presence of the fungus compared with non-inoculated control seedlings. The photosynthetic pigment content [chlorophyll (Chl) a, Chl b, and carotenoids] was significantly higher in P. indica-inoculated rice seedlings under high salt stress conditions as compared with salt-treated non-inoculated rice seedlings, in which these pigments were found to be decreased. Proline accumulation was also observed during P. indica colonization, which may help the inoculated plants to become salt tolerant. Taken together, P. indica rescues growth diminution of rice seedlings under salt stress.

Nano-technology for targeted drug delivery to combat antibiotic resistance

Several microbes have evolved clinically significant resistance against almost every available antibiotic. Yet the development of new classes of antibiotics has lagged far behind our growing need. Frequent and suboptimal use of antibiotics particularly in developing countries aggravated the problem by increasing the rate of resistance. Therefore, developing new and multidimensional strategies to combat microbial infections is warranted. These include i) modification of existing antibiotics, ii) searching new and novel antibiotics, iii) development and improvement of antibiotics carrier system to reduce amount and frequency of antibiotic doses, iv) development of targeted antibiotic delivery systems. Here, the authors discuss trends and development of nano-materials and alternative antimicrobials to solve the problem of antibiotic resistance.

Epidemiology of Group B Streptococcus in developing countries.

Group B Streptococcus (GBS) causes pneumonia, meningitis and sepsis in neonates. The current distribution pattern of GBS serotypes in developing countries such as India, China and Brazil is not clear. In order to appropriately plan for vaccination programs to address the burden of this disease in these countries, prospective population based studies are urgently needed. In our discussions, we focused on India, China and Brazil because of the membership of our workgroup, but data on other countries are also presented here. Further studies in developing countries are needed so as to better formulate appropriate public health interventions.

Enhanced degradation of hexachlorocyclohexane isomers by Sphingomonas paucimobilis

Hexachlorocyclohexane (HCH) has been banned for use in technologically advanced countries; however, it is still in use in tropical countries like India. Earlier we reported the degradation of HCH isomers by Sphingomonas paucimobilis within 12 days of incubation. Here we report the role of different factors that could enhance the degradation rate of HCH isomers. We found that an increase in the cell number from 102 to 108 cells/ml resulted in an increased degradation rate of HCH isomers viz. α, β, γ, and δ-HCH. While α-HCH and γ-HCH disappeared completely from the medium within 3 days of incubation, a maximum of only 90% and 85% degradation was observed for β and δ-HCH, respectively. We have also observed that adapted cultures degraded HCH isomers more efficiently than did the normal cultures.

Fungal association and utilization of phosphate by plants: success, limitations, and future prospects

Phosphorus (P) is a major macronutrient for plant health and development. The available form of P is generally low in the rhizosphere even in fertile soils. A major proportion of applied phosphate (Pi) fertilizers in the soil become fixed into insoluble, unavailable forms, which restricts crop production throughout the world. Roots possess two distinct modes of P uptake from the soil, direct and indirect uptake. The direct uptake of P is facilitated by the plant’s own Pi transporters while indirect uptake occurs via mycorrhizal symbiosis, where the host plant obtains P primarily from the fungal partner, while the fungus benefits from plant-derived reduced carbon. So far, only one Pi transporter has been characterized from the mycorrhizal fungus Glomus versiforme. As arbuscular mycorrhizal fungi cannot be cultured axenically, their Pi transporter network is difficult to exploite for large scale sustainable agriculture. Alternatively, the root-colonizing endophytic fungus Piriformospora indica can grow axenically and provides strong growth-promoting activity during its symbiosis with a broad spectrum of plants. P. indica contains a high affinity Pi transporter (PiPT) involved in improving Pi nutrition levels in the host plant under P limiting conditions. As P. indica can be manipulated genetically, it opens new vistas to be used in P deficient fields.

Role of Pilus Proteins in Adherence and Invasion of Streptococcus agalactiae to the Lung and Cervical Epithelial Cells

Background: Pili have been shown to play a key role in the attachment. Results: Pilus proteins anti-SAN1518, GBS80, and GBS67 inhibited the adherence and invasion of GBS to the lung and cervical epithelial cells. Conclusion: Pilus protein contributes to the initial attachment and invasion of GBS. Significance: Pilus protein-based vaccine formulation can also be tested against GBS serotypes of India. Streptococcus agalactiae, or group B Streptococcus (GBS), is an important opportunistic pathogen that causes pneumonia, sepsis, and meningitis in neonates and severe diseases in immunocompromised adults. We have performed comparative genomics of prevalent GBS serotypes of Indian origin (i.e. Ia, III, V, and VII). Pilus-proteins were commonly found up-regulated, and their expression was studied by using antiserum for GBS80 (backbone protein of pilus island-I), GBS67 (ancillary protein of PI-2a), and SAN1518 (backbone protein of PI-2b) by whole cell and Western blot analysis. To check the role of pilus proteins in adherence and invasion, an inhibition assay was performed. Comparative immunoblotting experiments revealed that expression of pili proteins does not differ in geographically different selected serotypes, Ia and V, of India and the United States. In the case of A549 cells, we found that GBS VII invasion and adherence was inhibited by pilus protein-specific antiserum SAN1518 significantly (p < 0.001) by 88.5 and 91%, respectively. We found that mutant strains, deficient in the pilus proteins (Δgbs80 and Δsan1518) exhibit a significant decrease in adherence in the case of type Ia, III, and VII. In the case of type VII, we have found a 95% reduction in invasion when Δsan1518 was used with A549 cells. Because the pilus proteins were identified previously as vaccine candidates against GBS serotypes of developed countries, we also found their role in the attachment and invasion of GBS of Indian origin. Thus, the present work supports the idea of making a more effective pilus protein-based vaccine that can be used universally.