Effects of Carbon Dioxide on Growth and Maltose Fermentation by Bacteroides amylophilus

The requirement of carbon dioxide for growth of Bacteroides amylophilus is quantitatively similar to that of certain other rumen bacteria. Carbon dioxide could be replaced by bicarbonate, but not by formate or certain amino acids. Label from ¹⁴CO₂ was incorporated into the succinate produced during maltose fermentation by B. amylophilus, and during glucose fermentation by B. ruminicola, and during cellobiose fermentation by B. succinogenes. All of the incorporated label could be associated with the carboxyl function of the molecule. The depression in radioactivity per micromole of carbon in the succinate formed from the fermentation of uniformly labeled ¹⁴C-maltose by B. amylophilus was greater than would be expected if all of the succinate formed was produced via a direct CO₂ fixation pathway(s) involving phosphoenolpyruvate or pyruvate; the radioactivity per micromole of carbon suggests that as much as 60% of the total succinate results from a pathway(s) involving direct CO₂ fixation. Maltose fermentation by B. amylophilus was dependent upon CO₂ concentration, but CO₂ concentration could not be shown to influence either the fermentation end-product ratios or the proportion of total succinate formed attributable to CO₂ fixation.     

Plant gas exchange at high wind speeds

High altitude Rhododendron ferrugineum L. and Pinus cembra L. seedlings were exposed to winds at 15 meters per second for 24-hour periods. Wind-sensitive stomata of Rhododendron seedlings immediately initiated a closing response which resulted in decreased photosynthesis and an even greater reduction in transpiration. Stomatal aperture and transpiration rates of P. cembra were only slightly reduced by high speed winds. However, photosynthesis was substantially reduced because of changes in needle display to available irradiation.     

Zearalenone Production by Fusarium Species

One-hundred-and-thirteen isolates of Fusarium were tested for their ability to produce zearalenone on autoclaved corn. They belonged to the following species (number of producers per number tested): F. epispheria, (0/1); F. moniliforme, (0/8); Gibberella fujikuroi, (0/3); F. nivale, (0/7); F. oxysporum, (0/15); F. roseum, (31/51); F. solani, (0/9); F. tricinctum (3/19). The isolates of individual species produced the following amounts of zearalenone per gram of corn: 3 isolates of F. roseum (0.6 to 119 mug), 3 of F. roseum "Culmorum" (1 to 210 mug), 3 of F. roseum "Equiseti" (0.6 to 2.0 mug), F. roseum "Gibbosum" (115 to 175 mug), 21 of F. roseum "Graminearum" (0.2 to 230 mug), and 3 of F. tricinctum (0.2 to 6.0 mug). All isolates of F. roseum "Graminearum" which formed the perithecial stage of G. zeae (G. roseum) produced zearalenone. Production occurred by the wild but not the appressed cultural type. Zearalenone production by F. tricinctum was confirmed by a mouse bioassay.     

Some effects of uncouplers and inhibitors on growth and electron transport in rumen bacteria.

Uncouplers and inhibitors of electron transport affected growth and electron transport of rumen bacteria in various ways. Selenomonas ruminantium was not affected by inhibitor and uncoupler concentrations which affected growth and electron transport of Bacteroides ruminicola, B. succinogenes, and Butyrivibrio fibrisolvens. Inhibitors, when active, led to accumulation of reduced electron carriers before the site of action, but differences were found among organisms in the site of action of these inhibitors. Uncouplers reduced the glucose molar growth yields (Ygluc) of B. ruminicola, B. succinogenes, and B. fibrisolvens compared with those obtained without uncouplers. The extent of Ygluc reduction accompanying inhibitor exposure reflected electron transport chain structure. S. ruminantium appeared to obtain its adenosine 5'-triphosphate from substrate-level processes only. The other organisms studied appeared to obtain adenosine 5'-triphosphate both from substrate-level processes and from electron transport but differed in the amount of adenosine 5'-triphosphate obtained from glucose catabolism and in the proportions of adenosine 5'-triphosphate obtained from substrate-level reactions and electron transport.     

EFFECTS OF ULTRAVIOLET-B IRRADIANCES ON SOYBEAN. IV. LEAF ONTOGENY AS A FACTOR IN EVALUATING ULTRAVIOLET-B IRRADIANCE EFFECTS ON NET PHOTOSYNTHESIS

There has recently been concern that some anthropogenic atmospheric pollutants, such as chlorofluoromethanes, may result in a global reduction in stratospheric ozone. This would undoubtedly increase the level of ultraviolet radiation reaching the surface of the earth. Such an increase in solar ultraviolet irradiation might have important biological consequences. Unifoliate leaves of decapitated soybean plants were exposed to 0, 20, 50, and 90 effective mW m² UV-B_BE (weighted ultraviolet-B irradiance) from special lamps in a greenhouse. The effects of UV-B radiation were examined in leaves at three different ontogenetic stages: bud; one-third expanded, and fully expanded leaves. Leaf area expansion, net photosynthesis, specific leaf weight, chlorophyll concentrations, and acidified methanol extract absorbance were measured during the course of the study. These data revealed several generalizations concerning the relationship between leaf ontogeny and photosynthetic response to UV-B radiation: 1) The rate and duration of leaf expansion are affected by low levels of UV-B irradiation. 2) There appears to be a shift in the ontogenetic sequence of photosynthetic capacity as a function of leaf age. 3) This results in leaves of similar chronological ages being in different physiological stages of maturity.     

Reliable sampling method for analysis of the ecology of the human alimentary tract.

An intubation method has been developed that allows removal of a sample of human intestinal fluid within a short period of time, that avoids contamination, and that minimizes exposure of the sample to air. Preliminary results obtained with this method have shown that the stomach and duodenum are essentially sterile and that the bacterial population present in the remainder of the small intestine is similar to that described by previous workers except that Veillonella species were encountered frequently and Haemophilus species were also detected in the lower jejunum and ileum of some individuals.     

Calcium control of waveform in isolated flagellar axonemes of chlamydomonas

The effect of Ca(++) on the waveform of reactivated, isolated axonemes of chlamydomonas flagella was investigated. Flagella were detached and isolated by the dibucaine procedure and demembranated by treatment with the detergent Nonidet; the resulting axomenes lack the flagellar membrane and basal bodies. In Ca(++)-buffered reactivation solutions containing 10(-6) M or less free Ca(++), the axonemes beat with a highly asymmetrical, predominantly planar waveform that closely resembled that of in situ flagella of forward swimming cells. In solutions containing 10(-4) M Ca(++), the axonemes beat with a symmetrical waveform that was very similar to that of in situ flagella during backward swimming. In 10(-5) M Ca(++), the axonemes were predominantly quiescent, a state that appears to be closely associated with changes in axomenal waveform or direction of beat in many organisms. Experiments in which the concentrations of free Ca(++), not CaATP(--) complex were independently varied suggested that free Ca(++), not CaATP(--), was responsible for the observed changes. Analysis of the flagellar ATPases associated with the isolated axonemes and the nonidet- soluble membrane-matrix fraction obtained during preparation of the axonemes showed that the axonemes lacked the 3.0S Ca(++)-activated ATPase, almost all of which was recovered in the membrane-matrix fraction. These results indicate that free Ca(++) binds directly to an axonemal component to alter flagellar waveform, and that neither the 3.0S CaATPase nor the basal bodies are directly involved in this change.