Effect of rhamnolipid on the physicochemical properties and interaction of bacteria and fungi

Bacterial adhesion on surfaces is an essential initial step in promoting bacterial mobilization for soil bioremediation process. Modification of the cell surface is required to improve the adhesion of bacteria. The modification of physicochemical properties by rhamnolipid to Pseudomonas putida KT2442, Rhodococcus erythropolis 3586 and Aspergillus brasiliensis ATCC 16404 strains was analysed using contact angle measurements. The surface energy and total free energy of adhesion were calculated to predict the adhesion of both bacteria strains on the A. brasiliensis surface. The study of bacterial adhesion was carried out to evaluate experimental value with the theoretical results. Bacteria and fungi physicochemical properties were modified significantly when treated with rhamnolipid. The adhesion rate of P. putida improved by 16% with the addition of rhamnolipid (below 1 CMC), while the increase of rhamnolipid concentration beyond 1 CMC did not further enhance the bacterial adhesion. The addition of rhamnolipid did not affect the adhesion of R. erythropolis. A good relationship has been obtained in which water contact angle and surface energy of fungal surfaces are the major factors contributing to the bacterial adhesion. The adhesion is mainly driven by acid-base interaction. This finding provides insight to the role of physicochemical properties in controlling the bacterial adhesion on the fungal surface to enhance bacteria transport in soil bioremediation.

The application of surfactant colloidal gas aphrons to remediate contaminated soil: A review

Surfactant solutions have been frequently studied for soil remediation. However, since they are expensive, massive consumption of surfactant solution can constrain their application. Surfactant microbubbles, or colloidal gas aphrons (CGAs), can serve as cost effective alternatives of surfactant solution because the use of CGAs reduce the amount of surfactant consumption. Moreover, CGAs can also improve the contact with the contaminated environment due to their unique surface properties, e.g. containing 40-70% of gas, small size, large interfacial areas, water-like flow properties and buoyant rise velocities. In this review paper, the properties and flow character of CGAs in soil matrix reviewed due to their relevance to soil remediation process. A comprehensive overview of the application of CGAs in flushing off organic pollutants and heavy metals, and carrying oxygen, bacteria and dissolved materials for soil remediation were provided. This paper also highlighted the limitation of CGAs application and important future research scopes.

Cerebral white matter microstructural changes in isolated maxillofacial trauma and associated neuropsychological outcomes

Isolated traumatic maxillofacial injury without concomitant brain injury may cause delayed post-concussive symptoms. Early identification allows optimal diagnosis, prognostication, and therapeutic intervention. The aim of this prospective observational study was to investigate longitudinal microstructural changes of the white matter (WM) tracts based on diffusion tensor imaging (DTI) indices in patients with isolated maxillofacial injuries, immediately and 6 months post-trauma, and to correlate these DTI indices with neuropsychological changes observed. Twenty-one patients with isolated maxillofacial injuries and 21 age-matched controls were recruited. DTI was performed and indices were calculated for 50 WM tracts. The neuropsychological evaluation was done using the screening module of the Neuropsychological Assessment Battery. Patients were subjected to repeat DTI and neuropsychological evaluation at 6 months post-trauma. Reduced fractional anisotropy (FA) and increased median (MD) and radial diffusivity (RD) in the acute phase were seen in major association, projection, and commissural fibre bundles, indicative of vasogenic oedema. These changes correlated with attention and executive function deficits in the acute phase, as well as improvement in memory and visuospatial function in the chronic phase. Isolated maxillofacial trauma patients develop WM microstructural damage, which may impair cognitive performance acutely and over time. DTI indices can serve as predictive imaging biomarkers for long-term cognitive deficits in isolated maxillofacial injuries.

Membrane distillation of saline and oily water using nearly superhydrophobic PVDF membrane incorporated with SiO2 nanoparticles

Fat, oil and grease in wastewater generated from household kitchens, restaurants and food processing plants affect sewer systems, water resources and environment adversely. Hence, membrane distillation of saline and oily water was studied using a nearly superhydrophobic membrane developed in this work. Polyvinylidene fluoride (PVDF) membrane incorporated SiO₂ nanoparticles was synthesized via phase inversion with dual baths and modified using hexadecyltrimethoxy silane. The volume ratio of silane to ethanol was varied between 1:200 to 1:25. The membrane characteristics were examined using a goniometer, a porometer, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The PVDF-SiO₂ membrane modified using the volume ratio of 1:50 achieved the highest water contact angle of 141.6° and LEP of 2.642 bar. This membrane was further tested in membrane distillation to observe the permeate flux of distilled water, saline solution (1 M NaCl) as well as saline and oily solution (1 M NaCl; 1,000 ppm of palm oil). The modified PVDF/SiO₂ showed high permeate flux which is nearly four times of the permeate flux of neat PVDF membrane, but still susceptible of salt and oil fouling as shown in SEM images.

Insecticide susceptibility status of Anopheles koliensis (Diptera: Culicidae) in northeastern Irian Jaya, Indonesia

Anopheles koliensis, an important malaria vector in the interior region of Irian Jaya, Indonesia, was evaluated for susceptibility to three different insecticide compounds using the standard World Health Organization diagnostic test kit and pretreated impregnated papers. A series of tests were conducted in Arso PIR I, a transmigrant settlement 60 km south of Jayapura, from January 1988 to May 1989. All compounds were tested at the recommended diagnostic dosage and exposure time. An. koliensis were susceptible to 1.0% fenitrothion at two hour exposure (N = 358) and 5.0% malathion at one hour exposure (N = 371) after the 24-hour holding period. Significant resistance to DDT was observed in both the An. koliensis and Culex quinquefasciatus populations. Approximately 30% of the An. koliensis population (N = 468) was resistant to 4% DDT at both one and two hour exposures. These findings indicate that routine use of DDT in Arso PIR I for indoor residual house spraying may be of limited effectiveness, in part, because of physiological resistance. However, use of an alternative insecticide will be more expensive and might prove equally ineffective because of the exophilic behavior of the species. This is the first confirmed report from repeated observations of DDT resistance in An. koliensis from Indonesia.

Heightened transmission of stable malaria in an isolated population in the highlands of Irian Jaya, Indonesia

Malaria at an elevation of 1,500 meters is uncommon and is usually unstable when it occurs. To confirm reports of a recent increase in transmission of stable malaria in the Oksibil Valley, which is at an elevation of 1,250-1,500 meters in the Jayawijaya Mountains of Irian Jaya, Indonesia, five malariometric surveys were conducted in four villages between May 1990 and July 1991. A total of 3,380 blood smears, representative of 1,949 persons, was examined. Prevalence rates over the survey period were consistent in each of the four villages, averaging 10% for infants, 50% for children 1-4 years of age, 35% for those 5-9 years old, 28% for those 10-14 years old, and 16% for adults (greater than 15 years old). The spleen rate for the those less than five years old was 96%, with an average enlarged spleen score of 2.32. Plasmodium falciparum accounted for 55% of the infections in the valley, but P. vivax was the predominant species in those less than 10 years old. In the village of Kutdol at an elevation of 1,500 meters, P. malariae was identified in 43% of the positive smears. Four cases were diagnosed as P. ovale. Infection with P. falciparum without obvious clinical symptoms was common in both adults and children. Entomologic and epidemiologic data suggested that the recent upsurge in transmission coincided with the replacement of traditional village huts with the more modern social housing. This replacement required the extensive construction of drainage ditches, which inadvertently also served as additional vector breeding sites. We suspect that this manipulation of the environment, in an effort to improve the quality of life, created conditions conductive for heightened transmission of stable malaria.