Thiosulfate Reduction, an Important Physiological Feature Shared by Members of the Order Thermotogales

Several members of the order Thermotogales in the domain Bacteria, viz., Thermotoga neapolitana, Thermotoga maritima, Thermosipho africanus, Fervidobacterium islandicum, and Thermotoga strain SEBR 2665, an isolate from an oil well, reduced thiosulfate to sulfide. This reductive process enhanced cellular yields and growth rates of all the members but was more significant with the two hyperthermophiles T. neapolitana and T. maritima. This is the first report of such an occurrence in this group of thermophilic and hyperthermophilic anaerobic bacteria. The results suggest that thiosulfate reduction is important in the geochemical cycling of sulfur in anaerobic thermal environments such as the slightly acidic and neutral-pH volcanic hot springs and oil reservoirs.     

Reevaluating the classification of Halobacteroides and Haloanaerobacter species based on sequence comparisons of the 16S ribosomal RNA gene

Abstract The 16S rRNA gene (rDNA) sequence analysis of four halophilic anaerobes: Halobacteroides halobius, H. lacunaris, Haloanaerobacter (Hb.) chitinovorans and H. acetoethylicus confirmed that they were all members of the family Haloanaerobiaceae. H. lacunaris and H. halobius were found to be more closely related to each other and were distantly related to Sporohalobacter lortetti and the members of the genera Haloanaerobium and Halothermothrix . These data are in agreement with their assignment to the genus Halobacteroides . Further analysis indicated that Hb. chitinovorans was closely affiliated to members of the genus Halobacteroides , and therefore we propose to transfer it to the genus Halobacteroides as H. chitinovorans comb. nov. This transfer would invalidate the genus Haloanaerobacter , as Hb. chitinovorans is the only member of this genus. The 16S rDNA sequence analysis of H. acetoethylicum indicated that it was very closely related to members of the genus Haloanaerobium , viz. Haloanaerobium (Ha.) praevalens, Ha. salsugo , and Ha. alcaliphilum , and hence we propose to transfer it to the genus Haloanaerobium as Ha. acetoethylicus comb. nov.     

Anaerobic digestion of sugar beet pulps

Summary Anaerobic digestion of sugar beet pulps was studied in a 70 l digestor with sequential feeding, after enzymatic hydrolysis by Trichoderma harzianum cellulases. During the 130 days feeding, 3.6 m³ of biogas were produced with an average content of 58% CH₄ from 270 l of hydrolysed pulps at 20 g VS/l. Average yield and production rate were respectively 0.67 m³/kg VS and 0.4 m³/ kg VS and 0.4 m³/m³ of digestor per day.     

Voltage-dependent proton fluxes in liposomes

Liposomes containing buffered KCl were prepared from bacterial lipids, were diluted into K+-free media and were treated with valinomycin to induce the formation of a diffusion potential (delta psi). Upon formation of such a potential, substantial proton influx was observed, as assayed by the quenching of 9-aminoacridine fluorescence. Complete reversal of fluorescence quenching occurred when the potential was collapsed by addition of KCl or when methylamine was added. Studies of proton influx as a function of the theoretical magnitude of the delta psi indicated that the phenomenon occurred only above a delta psi of about -60 mV. Establishment of a Na+ diffusion potential also resulted in proton influx. Treatment of K+-loaded liposomes with N,N'-dicyclohexylcarbodiimide did not reduce the delta psi-dependent proton influx. Moreover, proton influx could be demonstrated upon imposition of a diffusion potential in liposomes prepared from a synthetic lipid. The proton fluxes associated with generation of a diffusion potential in liposomes may complicate studies of reconstituted systems in which proton translocation should occur, and may affect the magnitude of the electrochemical proton gradient that is operant under some conditions.     

Similar growth pattern of mouse mammary epithelium cultivated in collagen matrix in vivo and in vitro

Mouse mammary ductal cells cultured in type I collagen gels give rise to three-dimensional multicellular outgrowths consisting of thin spikes which are often branched, and which may have pointed or blunt ends. The significance of these spikes to normal ductal morphogenesis has been unclear, since identical structures are not known to occur in vivo; conversely, it has not been possible to maintain in gel culture the highly structured end buds which are characteristic of ductal elongation in the animal. In order to evaluate whether the pattern of radiating spikes observed in collagen gel cultures results from chemical or physical peculiarities of the culture environment, a small volume of unpolymerized type I collagen solution was injected into mammary gland-free fat pads of young adult mice. After the bubble of collagen had polymerized, an implant of mammary ductal epithelium was introduced into the center of the gel. Histological examination of the implants after 3 to 6 days of growth revealed numerous small epithelial spikes, similar to those observed in gel culture, extending into the fibrous matrix. The early stages of regeneration of mammary implants placed in gland-free fat pads were then examined without the addition of exogenous collagen. In cases where the epithelium happened to contact a fibrous region of the fatty stroma, spikes were also seen to form in these natural collagenous substrates. Whether or not exogenous collagen was used, normal end buds were formed only when epithelial spikes contacted adipocytes. It was concluded that the three-dimensional pattern of radiating tubules in collagen gels in vitro is not merely an artifact of culture, but has a counterpart in vivo whereever regenerating mammary epithelium is surrounded by fibrous stroma. A model is presented in which the pattern of epithelial outgrowth is determined by the physical characteristics of the surrounding stroma; in collagen matrix a comparatively primitive and unspecialized type of morphogenesis occurs which may not require the participation of stromal cells. In contrast, epithelial-adipocyte interactions appear to be necessary for the formation of end buds and subsequent morphogenesis of fully structured mammary ducts.     

Effect of internal and external K+ on Na+−Ca2+ exchange in dialyzed squid axons under voltage clamp conditions

The effect of external and internal K⁺ on Na_o⁺-dependent Ca²⁺ efflux was studied in dialyzed squid axons under constant membrane potential. With axons clamped at their resting potentials, external K⁺ (up to 70 mM) has no effect on Na⁺?Ca²⁺ exchange. Removal of K_i⁺ causes a marked inhibition in the Na_o⁺-dependent Ca²⁺ efflux component. Internal K⁺ activates the Na⁺?Ca²⁺ exchange with low affinity $\text{(K}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 90 mM)}$. Activation by K_i⁺ is similar in the presence or in the absence of Na_i⁺, thus ruling out a displacement of Na_i⁺ from its inhibitory site. Axons dialyzed with ATP also show a dependency of Ca²⁺ efflux on K_i⁺. The present results demonstrate that K_i⁺ is an important cofactor (partially required) for the proper functioning of the forward Na⁺?Ca²⁺ exchange.     

S-adenosylmethionine and morphogenesis inMucor racemosus

The intracellular concentration of S-adenosylmethionine (SAM) and the specific activity of S-adenosylmethionine synthetase (ATP:l-methionine S-adenosyltransferase, EC 2.5.1.6) were examined in wild-typeMucor racemosus, as well as a morphological mutant termedcoy, under conditions designed to prevent the morphogenesis of yeasts to hyphae. When the mutant was grown in a defined medium supplemented with methionine and induced to shift by exposure to air, there was an increase in intracellular SAM analogous to that previously reported with the wild type. However, when thecoy mutant was grown in the absence of methionine, the intracellular concentration decreased dramatically and the mutant failed to undergo the yeast to hypha transition. An inhibitor of SAM synthetase activity, cycloserine, was used to lower the intracellular concentration of SAM in the wild-type organisms. Under these conditions, wild-typeM. racemosus failed to undergo the transition from yeasts to hyphae when exposed to air.     

Sexual preferences of male hamsters (Mesocricetus auratus) for conspecifics in different endocrine conditions

The behavioral responses of sexually experienced male hamsters toward a pair of anesthetized conspecifics were investigated. Males spent significantly more time licking, sniffing, and mounting neonatally and adult castrated males than intact males. Adult castrated males receiving oil injections were preferred over castrates receiving exogenous testosterone propionate (TP). Ovariectomized females were preferred over intact males, adult castrated males, or spayed females receiving exogenous TP. It was concluded that the absence of an androgen-dependent factor(s) renders an animal more sexually attractive.     

The nature of formate metabolism in greening barley leaves

The metabolism of [³H]formate has been examined in etiolated and greening leaves of barley (Hordeum vulgare), dwarf bean (Phaseolus vulgarls), broad bean (Vicia faba) and corn (Zea mays). Tritium was extensively incorporated by primary leaves incubated for 20-min periods in light or dark. The organic acids and free amino acids were the principal products of formate metabolism but these and other products were more heavily labelled in green tissues. Time course experiments with barley leaves revealed a rapid labelling of serine, accompanied by increasing amounts of ³H in glycine and aspartate as the feeding period was extended. These amino acid products were formed throughout a 4-day greening period with an approximate doubling in total incorporation being due to large accumulations of tritiated glycine and aspartate. The involvement of tetrahydrofolate-dependent reactions in formate metabolism was indicated by inhibition of [¹⁴C] and [³H]formate incorporation by the folate antagonist, aminopterin. Labelling of glycine and serine was also strongly inhibited (up to 90%) when the leaves were incubated with increasing concentrations of isonicotinylhydrazide.