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Abstracts of Recent Publications
Abstracts 1 2 3 4  

001- Noah Fierer, Zongzhi Liu, Mari Rodríguez-Hernández, Rob Knight, Matthew Henn, Mark T. Hernandez. University of Colorado, 216 UCB, CIRES, Boulder, CO 80309-0216. Short-Term Temporal Variability in Airborne Bacterial and Fungal Populations. Applied and Environmental Microbiology, 74, 2008, 200-207.

Airborne microorganisms have been studied for centuries, but the majority of this research has relied on cultivation-dependent surveys that may not capture all of the microbial diversity in the atmosphere. As a result, our understanding of airborne microbial ecology is limited despite the relevance of airborne microbes to human health, various ecosystem functions, and environmental quality.

Cultivation-independent surveys of small-subunit rRNA genes were conducted in order to identify the types of airborne bacteria and fungi found at a single site (Boulder, CO) and the temporal variability in the microbial assemblages over an 8-day period. We found that the air samples were dominated by ascomycete fungi of the Hypocreales order and a diverse array of bacteria, including members of the proteobacterial and Cytophaga-Flavobacterium-Bacteroides groups that are commonly found in comparable culture-independent surveys of airborne bacteria. Bacterium/fungus ratios varied by 2 orders of magnitude over the sampling period, and we observed large shifts in the phylogenetic diversity of bacteria present in the air samples collected on different dates, shifts that were not likely to be related to local meteorological conditions. We observed more phylogenetic similarity between bacteria collected from geographically distant sites than between bacteria collected from the same site on different days. These results suggest that outdoor air may harbor similar types of bacteria regardless of location and that the short-term temporal variability in airborne bacterial assemblages can be very large.

Keywords:Airborne Bacterial, Fungal Populations, Airborne microorganisms, airborne microbes, Hypocreales.


002-Luis David Alcaraz, Gabriela Olmedo, Germán Bonilla, René Cerritos, Gustavo Hernández, Alfredo Cruz, Enrique Ramírez, Catherine Putonti, Beatriz Jiménez, Eva Martínez, Varinia López, Jacqueline L. Arvizu, Francisco Ayala, Francisco Razo, Juan Caballero, Janet Siefert, Luis Eguiarte, Jean-Philippe Vielle, Octavio Martínez, Valeria Souza, Alfredo Herrera-Estrella, Luis Herrera-Estrella.The genome of Bacillus coahuilensis reveals adaptations essential for survival in the relic of an ancient marine environment. PNAS, 105, 2008, 5803-5808.

The Cuatro Ciénegas Basin (CCB) in the central part of the Chihuahan desert (Coahuila, Mexico) hosts a wide diversity of microorganisms contained within springs thought to be geomorphological relics of an ancient sea. A major question remaining to be answered is whether bacteria from CCB are ancient marine bacteria that adapted to an oligotrophic system poor in NaCl, rich in sulfates, and with extremely low phosphorus levels (<0.3 µM). Here, we report the complete genome sequence of Bacillus coahuilensis, a sporulating bacterium isolated from the water column of a desiccation lagoon in CCB. At 3.35 Megabases this is the smallest genome sequenced to date of a Bacillus species and provides insights into the origin, evolution, and adaptation of B. coahuilensis to the CCB environment. We propose that the size and complexity of the B. coahuilensis genome reflects the adaptation of an ancient marine bacterium to a novel environment, providing support to a "marine isolation origin hypothesis" that is consistent with the geology of CCB. This genomic adaptation includes the acquisition through horizontal gene transfer of genes involved in phosphorous utilization efficiency and adaptation to high-light environments. The B. coahuilensis genome sequence also revealed important ecological features of the bacterial community in CCB and offers opportunities for a unique glimpse of a microbe-dominated world last seen in the Precambrian.

Keywords: evolution, enomic adaptation, horizontal, gene transfer, phosphorus stress, sulfolipids, B. coahuilensis.


003- Virginia H. Dale, Aaron D. Peacock , Charles T. Garten Jr, Edward Sobek, Amy K. Wolfe. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA. Selecting indicators of soil, microbial, and plant conditions to understand ecological changes in Georgia pine forests. Ecological Indicators, 8, 2008, 818-827.

Characterizing how resource use and management activities affect ecological conditions is necessary to document and understand anthropogenic changes in ecological systems. Resource managers on military installations have the delicate task of balancing the training needs of soldiers effectively with the need to maintain a high quality of ecological conditions. This study considers ways that ecological indicators can provide information on impacts that training has on environmental characteristics that occur at different scales and in different sectors of the environment. The characteristics examined include soil chemistry, soil microbes, and vegetation. A discriminant function analysis was conducted to determine whether ecological indicators could differentiate among different levels of military use. A combination of 10 indicators explained 90% of the variation among plots from five different military use levels. Results indicated that an appropriate suite of ecological indicators for military resource managers includes soil, microbial, and vegetation characteristics. Since many of these indicators are related, managers at this location potentially have freedom to choose indicators that are relatively easy to measure, without sacrificing information.

Keywords: Indicators of soil, Georgia pine forests, soil microbes, microbial, ecological changes.


004-Yu-Hong Su, Yong-Guan Zhu. Research Center for Eco-environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Beijing 100085, China. Uptake of selected PAHs from contaminated soils by rice seedlings (Oryza sativa) and influence of rhizosphere on PAH distribution. Environmental Pollution, 155, 2008, 359-365.

The uptake of selected polycyclic aromatic hydrocarbons (PAHs) by rice (Oryza sativa) seedlings from spiked aged soils was investigated.When applied to soils aged for 4 months, naphthalene, phenanthrene, and pyrene exhibited volatilization loss of 98, 95, and 30%, respectively,with the remaining fraction being fixed by soil organic matter and/or degraded by soil microbes. In general, concentrations of the three PAHs in rice roots were greater than those in the shoots. The concentrations of root associated PHN and PYR increased proportionally with both soil solution and rhizosphere concentrations. PAH concentrations in shoots were largely independent of those in soil solution, rice roots, or rhizosphere soil. The relative contributions of plant uptake and plant-promoted rhizosphere microbial biodegradation to the total mass balance were 0.24 and 14%, respectively, based on PYR concentrations in rhizosphere and non-rhizosphere soils, the biomass of rice roots, and the dry soil weight.

Keywords:PAHs; Rice (Oryza sativa); Uptake; Rhizosphere effect; Aged soil.


ENVIS CENTRE Newsletter Vol.7,Issue 1 January 2009 Back
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