Iron reduction by psychotrophic enrichment cultures

Psychrotrophic (<20 degrees C) enrichment cultures from deep Pacific marine sediments and Alaskan tundra permafrost reduced ferric iron when using org anic acids or H-2 as electron donors. The representative culture W3-7 from the Pacific sediments grew fastest at 10 degrees C, which was 5-fold faster than at 25 degrees C and more than 40-fold faster than at 4 degrees C. Fe( III) reduction was also the fastest at 10 degrees C, which was 2-fold faste r than at 25 degrees C and 12-fold faster than at 4 degrees C. Overall, abo ut 80% of the enrichment cultures exhibited microbial Fe(III) reduction und er psychrotrophic conditions. These results indicated that microbial iron r eduction is likely widespread in cold natural environments and may play imp ortant roles in cycling of iron and organic matter over geological times. ( C) 1999 Published by Elsevier Science B.V. All rights reserved.