Marine crude-oil biodegradation: a central role for interspecies interactions

ABSTRACT: The marine environment is highly susceptible to pollution by petroleum, and so it is important to understand how microorganisms degrade hydrocarbons, and thereby mitigate ecosystem damage. Our understanding about the ecology, physiology, biochemistry and genetics of oil-degrading bacteria and fungi has increased greatly in recent decades; however, individual populations of microbes do not function alone in nature. The diverse array of hydrocarbons present in crude oil requires resource partitioning by microbial populations, and microbial modification of oil components and the surrounding environment will lead to temporal succession. But even when just one type of hydrocarbon is present, a network of direct and indirect interactions within and between species is observed. In this review we consider competition for resources, but focus on some of the key cooperative interactions: consumption of metabolites, biosurfactant production, provision of oxygen and fixed nitrogen. The emphasis is largely on aerobic processes, and especially interactions between bacteria, fungi and microalgae. The self-construction of a functioning community is central to microbial success, and learning how such "microbial modules" interact will be pivotal to enhancing biotechnological processes, including the bioremediation of hydrocarbons.     

Zooplankton associations and environmental factors in Ogunpa and Ona rivers, Nigeria

Zooplankton abundance, composition and environmental parameters were monitored in two tropical rivers over a twenty month period. The data was subjected to cluster, factor and correlation analysis to determine the grouping pattern of zooplankton and their relationship to environmental parameters. Environmental factors in Ogunpa and Ona rivers--included buffering capacity, trace metal ions, pH-temperature/transparency--were primarily influenced by rainfall. The dominance of the Rotifera in both rivers was attributed to their short developmental rate and fish predation on larger zooplankton. Two groups of associations were identified in each river--a commonly occurring species group exhibiting strong homogenous correlation with environmental factors and a predominant group exhibiting weak correlation with environmental factors and whose abundance/composition may be defined by biotic factors.     

Heavy metal tolerance potential of Aspergillus strains isolated from mining sites

Increased heavy metal pollution generated through anthropogenic activities into the environment has necessitated the need for eco-friendly remediation strategies such as mycoremediation. With a view to prospecting for fungi with heavy metal remediation potentials, the tolerance of five Aspergillus species isolated from soils of three active gold and gemstone mining sites in southwestern Nigeria to varied heavy metal concentrations was investigated. Isolated Aspergillus strains were identified based on the internal transcribed spacer 1 and 2 (ITS 1 and ITS 2) regions. Growth of Aspergillus strains were challenged with a range of varied concentrations of heavy metals: cadmium (Cd) (0–100), copper (Cu) (0–1000), lead (Pb) (0–400), arsenic (As) (0–500), and iron (Fe) (0–800) concentrations (ppm) incorporated into Malt Extract Agar (MEA) in triplicates. Mycelial radial growths were recorded at intervals of 3 days during a 13-day incubation period. Aspergillus strains were identified as A. tubingensis, A. fumigatus, A. terreus, A. nidulans, and A. nomius. A. tubingensis tolerated Cd, Cu, Pb, As, and Fe at all test concentrations (100–1000 ppm), showing no significant (p > .05) difference compared with the control. Similarly, A. nomius tolerated all concentrations of Cu, Pb, As, and Fe and only 50 ppm Cd concentrations. A. nidulans, A. terreus, and A. fumigatus, on the other hand, tolerated all concentrations of Cu, Pb, and Fe with no statistical significance (p > .05) difference from the controls. Overall, the Aspergillus species showed tolerance to heavy metal concentrations above permissible limits for contaminated soils globally. These heavy metal tolerance traits exhibited by the Aspergillus isolates may suggest that they are potential candidates for bioremediation of heavy metal–polluted environments.     

From Single Cells to Tissues: Interactions between the Matrix and Human Breast Cells in Real Time

Background

Mammary gland morphogenesis involves ductal elongation, branching, and budding. All of these processes are mediated by stroma - epithelium interactions. Biomechanical factors, such as matrix stiffness, have been established as important factors in these interactions. For example, epithelial cells fail to form normal acinar structures in vitro in 3D gels that exceed the stiffness of a normal mammary gland. Additionally, heterogeneity in the spatial distribution of acini and ducts within individual collagen gels suggests that local organization of the matrix may guide morphogenesis. Here, we quantified the effects of both bulk material stiffness and local collagen fiber arrangement on epithelial morphogenesis.

Results

The formation of ducts and acini from single cells and the reorganization of the collagen fiber network were quantified using time-lapse confocal microscopy. MCF10A cells organized the surrounding collagen fibers during the first twelve hours after seeding. Collagen fiber density and alignment relative to the epithelial surface significantly increased within the first twelve hours and were a major influence in the shaping of the mammary epithelium. The addition of Matrigel to the collagen fiber network impaired cell-mediated reorganization of the matrix and increased the probability of spheroidal acini rather than branching ducts. The mechanical anisotropy created by regions of highly aligned collagen fibers facilitated elongation and branching, which was significantly correlated with fiber organization. In contrast, changes in bulk stiffness were not a strong predictor of this epithelial morphology.

Conclusions

Localized regions of collagen fiber alignment are required for ductal elongation and branching suggesting the importance of local mechanical anisotropy in mammary epithelial morphogenesis. Similar principles may govern the morphology of branching and budding in other tissues and organs.