Structure elucidation and proposed de novo synthesis of an unusual mono-rhamnolipid by Pseudomonas guguanensis from Chennai Port area.

In this paper, we describe the isolation of an unusual type of high molecular weight monorhamnolipid attached to esters of palmitic, stearic, hexa and octadecanoic acids as against the routinely reported di-rhamnolipids linked to hydroxydecanoic acids. The bioemulsifier was column-purified and the chemical nature of the compound was elucidated using FT-IR, GC-MS and 1D [1H and13C] and 2D NMR. This monorhamnolipid is extracted from a bacterium, Pseudomonas guganensis and is not reported to have biological activities, let alone emulsification abilities. The bacterium continually produced rhamnolipids when nourished with n-hexadecane as its lone carbon source. The extracellularly secreted monorhamnolipids are capable of degrading hydrocarbons, with most preference to n-hexadecane [EI24 of 56 ± 1.42% by 2 mL of the spent medium]. Whilst the crude ethyl acetate partitioned extract had an EI24 of 65 ± 1.43%; the purified rhamnolipid product showed 78 ± 1.75% both at 12.5 mg/mL concentration. The used-up n-hexadecane is biotransformed to prepare its own rhamnolipids which in return is utilized to degrade n-alkanes thus creating a circular pathway which is proposed herein. This bacterium can be seen as a new source of bioemulsifier to reduce hydrocarbon in polluted waters.

Bioremediation of a pentacyclic PAH, Dibenz(a,h)Anthracene- A long road to trip with bacteria, fungi, autotrophic eukaryotes and surprises.

Dibenz(a,h)Anthracene (DBahA), classified as a probable human carcinogen (B2) is the first Poly Aromatic Hydrocarbons (PAH) to be chemically purified and used for cancer-based studies. Till date, only 30 papers focus on the bioremediation aspects of DBahA out of more than 200 research publications for each of the other 15 priority PAHs. Thus, the review raises an alarm and calls for efficient bioremediation strategies for considerable elimination of this compound from the environment. This article reviews and segregates the available papers on DBahA bioremoval from the beginning till date into bacteria, fungi and plant-mediated remediation and offers suggestions for the most competent and cost-effective modes to bioremove DBahA from the environment. One of the proficient ways to get rid of this PAH could with the use of biosurfactant-enriched bacterial consortium in DBahA polluted environment, which is given considerable importance here. Among the bacterial and fungal microbiomes, unquestionably the former are the beneficiaries which utilize the breakdown products of this PAH metabolized by the latter. Nevertheless, the use of plant communities for efficient DBahA utilization through fibrous root system is also discussed at length. The current status of DBahA as reflected by the publications at https://www.ncbi.nlm.nih.gov and recommendations among the explored groups [bacterial/fungal/plant communities] for better DBahA elimination are pointed out. Finally, the review emphasizes the pros and cons of all the methodologies used for selective/combinatorial removal of DBahA and present the domain to the researchers to carry forward by incorporating their individual ideas.

Demonstration of bioprocess factors optimization for enhanced mono-rhamnolipid production by a marine Pseudomonas guguanensis.

We identified that Pseudomonas guguanensis produced macromolecular mono-rhamnolipid (1264.52 Da) upon sensing n-hexadecane/diesel/kerosene from its surroundings. Permutation experiments were done to improve the laboratory-scale mono-rhamnolipid production (ie, a three-fold increase) using RSM validation. Consequently, maximal mono-rhamnolipids production [40-50 mg/L] and emulsification abilities [65-70%] were encountered on day 8 using vegetable oil, peptone + yeast extract. EI24 values for the rhamnolipids were found to be 78±1.75% at 12.5 mg/ mL. Production and secretion of rhamnolipids were accompanied by aggregation of cells at day 6 as pictured in SEM. Pure monorhamnolipids of P. guguanensis was found to lower the surface tension of water to 32.98±0.3 mN/m than the crude and CFSs of P. aeruginosa indicating efficient activity. Utilization and subsequent removal of hexadecane was 77.2% and the breakdown products were fatty acids [decanoic, hexadecanoic, octadecanoic acids and methyl stearates] as signified in Head-space GC-MS. The breakdown products of hexadecane are also present in the synthesized rhamnolipids suggesting their biosynthetic role. Rapid degradation of hexadecane, diesel and kerosene by this emulsifier combined with non-pathogenic trait of P. guguanensis identifies this organism as a viable option to remove n-alkanes from aquatic environments.

Delineation of large deletions of the MECP2 gene in Rett syndrome patients, including a familial case with a male proband.

Comprehensive genetic screening programs have led to the identification of pathogenic methyl-CpG-binding protein 2 (MECP2) mutations in up to 95% of classical Rett syndrome (RTT) patients. This high rate of mutation detection can partly be attributed to specialised techniques that have enabled the detection of large deletions in a substantial fraction of otherwise mutation-negative patients. These cases would normally be missed by the routine PCR-based screening strategies. Here, we have identified large multi-exonic deletions in 12/149 apparently mutation-negative RTT patients using multiplex ligation-dependent probe amplification (MLPA). These deletions were subsequently characterised using real-time quantitative PCR (qPCR) and long-range PCR with the ultimate aim of defining the exact nucleotide positions of the breakpoints and rearrangements. We detected an apparent deletion in one further patient using MLPA; however, this finding was contradicted by subsequent qPCR and long-range PCR results. The patient group includes an affected brother and sister with a large MECP2 deletion also present in their carrier mother. The X chromosome inactivation pattern of all female patients in this study was determined, which, coupled with detailed clinical information, allowed meaningful genotype-phenotype correlations to be drawn. This study reaffirms the view that large MECP2 deletions are an important cause of both classical and atypical RTT syndrome, and cautions that apparent deletions detected using high-throughput diagnostic techniques require further characterisation.