Characterization of the indigenous PAH-degrading bacteria of Spartina dominated salt marshes in the New York/New Jersey Harbor.

The aerobic polyaromatic hydrocarbon (PAH) degrading microbial communities of two petroleum-impacted Spartina-dominated salt marshes in the New York/New Jersey Harbor were examined using a combination of microbiological, molecular and chemical techniques. Microbial isolation studies resulted in the identification of 48 aromatic hydrocarbon-degrading bacterial strains from both vegetated and non-vegetated marsh sediments. The majority of the isolates were from the genera Paenibacillus and Pseudomonas. Radiotracer studies using (14)C-phenanthrene and (14)C-pyrene were used to measure the PAH-mineralization activity in salt marsh sediments. The results suggested a trend towards increased PAH mineralization in vegetated sediments relative to non-vegetated sediments. This trend was supported by the enumeration of PAH-degrading bacteria in non-vegetated and vegetated sediment using a Most Probable Numbers (MPN) technique, which demonstrated that PAH-degrading bacteria existed in non-vegetated and vegetated sediments at levels ranging from 10(2 )to 10(5 )cells/g sediment respectively. No difference between microbial communities present in vegetated versus non-vegetated sediments was found using terminal restriction fragment length polymorphism (of the 16S rRNA gene) or phospholipid fatty acid analysis. These studies provide information on the specific members and activity of the PAH-degrading aerobic bacterial communities present in Spartina-dominated salt marshes in the New York/New Jersey Harbor estuary.

Working memory in spelling: evidence from backward typing.

Theories of spelling (Margolin, 1984; Nolan & Caramazza, 1983) propose a working memory system for storing order and identity information of letters during the spelling process. Capacity limitations related to the use of such a graphemic buffer were explored. Participants had to type words backwards. Longer pauses between key presses were assumed to signal points at which graphemic buffer contents were refreshed. Five- and six-letter words were divided by a major pause into chunks of two and three letters, partly coinciding with syllables. Articulatory suppression had no effect on performance. Increasing the length of the stimuli to seven to eight letters resulted in major pauses occurring at syllable boundaries, and performance becoming vulnerable to articulatory suppression but not foot tapping. Forward typing resulted in a similar pause pattern. The results suggest that chunks of approximately three letters can be handled at any one time. For short words the task seems to rely on non-phonological modes of coding, whereas longer words appear to require the use of a phonological code, possibly for keeping track of progress through the word.

Influence of microbes on the mobilization, toxicity and biomethylation of arsenic in soil.

To understand the effects of microbial activity on the mobilization and speciation of arsenic in soil, the cycling of arsenic was studied in microcosm experiments under laboratory conditions. Particular attention was paid to the biomethylation of arsenic and to the toxicity of inorganic and organic arsenic species for microbes. Microbes enhanced mobilization of arsenic from soil by 19-24% compared to formaldehyde inhibited controls. Formation of dissolved methylated arsenic species by microbes was low (< 0.1%) during the 5-day incubation. Even though methylation may function as a detoxification method, it was of minor importance in the soil tested.