An anaerobic, mesophilic, spore-forming, cellulolytic bacterium was repeatedly isolated from a woodfermenting anaerobic digester. Cells of this organism were gram-positive rods, motile with a bundle of polar flagella, and formed subterminal oblong spores. The colonies in agar had an irregular shape with many platelike structures and were greyish white. Cellulose, xylan, and cellobiose served as substrates for growth. Acetate, propionate, butyrate, isobutyrate, isovalerate, lactate, succinate, H,, and CO, were products of cellobiose fermentation. The optimal temperature and pH for growth were 35°C and 7, respectively. The DNA composition was 40 mol% G+C. The name Clostridium aldn'chii sp. nov. is proposed. The type strain is P-1 (= OGI 112, = ATCC 49358).Woody biomass generally was not considered to be biodegradable under anaerobic conditions until Zeikus and Ward (22) showed that a methane fermentation occurs in the heartwood of live trees and Chynoweth and co-workers (4, 9) showed that the carbohydrates of poplar and other hardwoods are degraded to methane by a domestic sludge digester inoculum without pretreatment other than reduction of particle size to the millimeter range. These observations have stimulated research to determine the organisms and interactions involved with the possible goal of improving the extent and rate of these depolymerization reactions. Sleat and co-workers (18, 19) have isolated two new cellulolytic, Clostridium species from wood methane fermentation. Our laboratory has begun to isolate predominant cellulolytic pectinolytic, and xylanolytic bacteria from poplar-fed wood digesters. The first of these, a new cellulolytic Clostridium species, has been repeatedly isolated from high dilutions of the samples over a period of 2 years and is described below. The name Clostridium aldrichii is proposed for this organism. MATERIALS AND METHODSSamples and treatments. Strict anaerobic methods (7) were used for sample collection, medium preparation, inoculation, and identification. Samples were collected from the effluent of a continuously stirred tank, bench-scale, mesophilic (35°C)) poplar-fed digester. The effluent was blended for less than 1 min in a homogenizer under oxygen-free N,-CO, (80:20). The treated sample was diluted in basal medium up to lo-'' in order to exceed the highest dilution with cellulolytic activity. The first sample was collected 65 days after the digester was started.

Monoclonal antibodies (Mabs) against Clostridium aldrichii were prepared by in vivo and in vitro immunization with whole cells and produced after fusion as ascites in BALB/c mice. An enzyme-linked immunosorbent assay (ELISA) was used to test for specificity and sensitivity of the Mabs to detect Cl. aldrichii. The lower limit for Cl. aldrichii detection in pure and mixed culture with ELISA was 10(5) cells ml-1. Twenty other species of bacteria, including 12 cellulolytic species, were tested for cross-reactivity with the ELISA, but none was detected. The ELISA was used for detection of Cl. aldrichii over a 16-month period in five mesophilic continuously-stirred tank reactors (CSTR) with wood, glucose, sludge or sorghum as substrates. The population of Cl. aldrichii in the poplar wood anaerobic digester effluent was 10(6)-10(7) cells ml-1 over that time. These numbers were confirmed by anaerobic microbiological methods. Results from the ELISA technique were obtained in 36 h vs 3 weeks for culture methods. It is concluded that the ELISA is a useful, time-saving method for identification, detection and quantification of Cl. aldrichii in axenic, mixed culture, and in complex undefined cultures such as those found in anaerobic digesters.

A monoclonal antibody (mAb) was raised against Fibrobacter succinogenes and produced after fusion as ascites in BALB/c mice. An ELISA was used to test for specificity and sensitivity of the mAb to detect F. succinogenes. The mAb BD1 was tested for sensitivity and cross-reactivity in detecting F. succinogenes with ELISA. The lower limits for F. succinogenes detection in pure and mixed culture-using mAb BD1 with ELISA was 10(5) cells ml-1. Twenty-six other species of bacteria, including 12 cellulolytic species, were tested for cross-reactivity with the ELISA but none was detected. Electron micrographs of F. succinogenes cells with immunogold labelling showed that the mAb BD1 reacted exclusively with cell wall epitopes but not intracellular material, as confirmed by ELISA.