Clostridium thermoaceticum ATCC 39073 converted vanillate to catechol. Although carboxylated aromatic compounds which did not contain methoxyl groups were not by themselves growth supportive, protocatechuate and p-hydroxybenzoate (nonmethoxylated aromatic compounds) were converted to catechol and phenol, respectively, during carbon monoxide-dependent growth. Syringate is not subject to decarboxylation by C. thermoaceticum (Z. Wu, S. L. Daniel, and H. L. Drake, J. Bacteriol. 170:5705-5708, 1988), and sustained growth at the expense of syringate-derived methoxyl groups was dependent on supplemental CO2. In contrast, vanillate was growth supportive in the absence of supplemental CO2, and 14CO2 was the major 14C-labeled product during [carboxyl-14C]vanillate-dependent growth. Furthermore, the decarboxylation of protocatechuate and p-hydroxybenzoate supported methanol- and 1,2,3-trimethoxybenzene-dependent growth (CO2 is required for growth at the expense of these substrates) when supplemental CO2 was depleted from the growth medium, and the decarboxylation of protocatechuate was concomitant with improved cell yields of methanol cultures. These findings demonstrate that (i) C. thermoaceticum is competent in the decarboxylation of certain aromatic compounds and (ii) under certain conditions, decarboxylation may be integrated to the flow of carbon and energy during acetogenesis.
: 1990). By using 4-hydroxybenzoate as a model substrate, an assay was devel9ped to study the expression apd activity of the decarboxylase involved in the activa'tion of aromatic carboxyl groups. The aromatic-dppendent decarboxylase was induced by carboxylated aromatic compounds in the early'stages of'growth and was not repressed by glucose or. other acetogenic substrates; nonutilizable carboxylated aromatic compounds did not induce the decarboxylase. The decarboxylase activity displayed saturation kinetics at both whole-cell and cell extract levels, was sensitive to oxidation, and was not affected by exogenous energy sources. However, at the whole-cell level, metabolic inhibitors decreased the decarboxylase activity. Supplemental biotin or avidin did not significantly affect decarboxylation. The aromatic-dependent decarboxylase was specific for benzoates with a hydroxyl group in the para position of the aromatic ring; the meta position could bie occupied by various substituent groups (-H, -OH, -OCH3, -Cl, or -F). The carboxyl carbon from [carboxyl-'4C]vaniliate went primarily to 14C02 in short-term decarboxylase assays. During growth, the aromatic carboxyl group went primarily to CO2 under C02-enriched conditions. However, under C02-limited conditions, the aromatic carboxyl carbon went nearly totally to acetate, with equal distribution between the carboxyl and methyl carbons, thus demonstrating that acetate could be totally synthesized from aromatic carboxyl groups. In contrast, when cocultivated (i.e., supplemented) with CO under C02-limited conditions, the aromatic carboxyl group went primarily to the methyl carbon of acetate.
Vanillin was subjet to O demethylation and supported growth of Clostridium formicoaceticum and Clostridium thermoaceticum. Vanillin was also stimulatory to the CO‐dependent growth of Peptostreptococcus productus. the aldehyde substituent of vanillin was metabolized by routes which were dependent upon both the acetogen and a co‐metabolizable substrate (e.g. carbon monoxide [CO]). C. formicoaceticum and C. thermoaceticum oxidized the aldehyde group of vanillin to the carboxyl level, while P. productus reduced the aldehyde group of vanillin to the alcohol level. In contrast, during CO‐dependent growth, C. thermoaceticum reduced 4‐hydroxybenzaldehyde to 4‐hydroxylbenzyl alcohol while P. productus both reduced and oxidized 4‐hydroxybenzaldehyde to 4‐hydroxybenzyl alcohol and 4‐hydroxybenzoate, respectively. These metabolic potentials indicate aromatic aldehydes may affect the flow of reductant during acetogenesis.
Vanillin was subject to O demethylation and supported growth of Clostridium formicoaceticum and Clostridium thermoaceticum. Vanillin was also stimulatory to the CO-dependent growth of Peptostreptococcus productus. The aldehyde substituent of vanillin was metabolized by routes which were dependent upon both the acetogen and a co-metabolizable substrate (e.g. carbon monoxide [CO]). C. formicoaceticum and C. thermoaceticum oxidized the aldehyde group of vanillin to the carboxyl level, while P. productus reduced the aldehyde group of vanillin to the alcohol level. In contrast, during CO-dependent growth, C. thermoaceticum reduced 4-hydroxybenzaldehyde to 4-hydroxybenzyl alcohol while P. productus both reduced and oxidized 4-hydroxybenzaldehyde to 4-hydroxybenzyl alcohol and 4-hydroxybenzoate, respectively. These metabolic potentials indicate aromatic aldehydes may affect the flow of reductant during acetogenesis.
Microbiology is offered each semester at the Allied Health Campus of Pearl River Community College. The evening course meets weekly for 16 sessions from 5 p.m. to 10 p.m. Most students enrolled in the course are in one of the seven associate degree allied health programs on the allied health campus. Among the challenges of teaching a course in this situation is retention of enrolled students. Although the course is required for most of the allied health programs on the campus, many students enrolled, attended class for a few weeks, and withdrew from the course. During the 1998-1999 school year the retention rates for students enrolled in the night microbiology classes for Fall and Spring semesters were 52% and 47%, respectively. The format for the 1998-1999 academic year was a conventional course with 2½ hours of lecture material followed by 2 hours of laboratory. Little or no effort was made to correlate laboratory and lecture topics. The course format for Fall 1999 was modified to (i) provide the laboratory component at the beginning of the time slot, (ii) tailor the lecture topics to relate to the laboratory component each night, and (iii) add an outside reading component. The laboratory served as an introduction to the lecture topic, and the lecture became more significant since it related directly to the laboratory experience. Following this format change the retention rate for the Fall 1999 semester increased to 80%.
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