Fine Structural Changes of Acetobacter suboxydans During Growth in a Defined Medium

Abstract

Cytological differences were observed between stationary-and exponentialphase cells of Acetobacter suboxydans grown in a defined medium. Unstained cells observed with the light microscope just after entering the stationary phase differed from exponentially growing cells in that the former exhibited localized increases in density, particularly in the polar regions. Electron microscopy of thin sections revealed that early stationary-phase cells possessed predominantly polar complexes of intracytoplasmic membranes accompanied by polar increases in ribosomal material. When cultures were allowed to continue far into the stationary phase, cells contained extensive aggregations of membrane-like material as the predominant fine-structural feature. In contrast, thin sections of exponentially growing cells exhibited only occasional indications of intracytoplasmic membranes. Intracytoplasmic membranes heretofore have been observed only rarely in the heterotrophic Pseudomonadales.

Effect of Intracytoplasmic Membrane Development on Oxidation of Sorbitol and Other Polyols by Gluconobacter oxydans

“…Our previously published data (3,7) together with that published here show that (i) the intra- The optimum pH of 5.0 is low compared with that which is reportedly optimum for growth (pH 6.0). However, this bacterium is known to readily initiate growth at pH 4.5 (10), indicating that the optimum pH for sorbitol oxidation is well within the physiological range for this acidtolerant bacterium.…”

“…For cells to have greater respiration rates at a time when their energy needs were decreasing seemed to contradict the idea that limited oxidation functioned solely for energy generation. We found that this increase in oxidative activity was paralleled by the formation of intracytoplasmic membranes (3,7) and an increase in cellular phospholipids (18). Evidenced from thin sections (7) and qualitative fatty-acid analyses (19) strongly suggested that these intracytoplasmic membranes resulted from continued synthesis and subsequent convolution of the plasma membrane after cell division stopped.…”

“…Of the non-photosynthetic gram-negative procaryotes, complex intracytoplasmic membranes are formed most notably by four physiological groups: Azotobacter (29,30), Gluconobacter (3,7), the obligate methane and methanol oxidizers (9,32,36,37,43), and the ammo- Assay procedures and growth conditions were as described in the text and in the legend to Fig. 1.…”

“…However, we were aware that alternate explanations were also possible. For example, all of our previous studies (3,7,18,19) used glycerol-grown cells, and it was conceivable that continued phospholipid and plasma membrane synthesis occurred only when cells were grown in media containing glycerol. It was also possible that increased respiration rates were due to increased quantities of soluble polyol dehydrogenases or caused by changes in allosteric controls as cells shifted from exponential growth to the stationary phase.…”

Isolation and characterization of membranes from a hydrocarbon-oxidizing Acinetobacter sp

“…Mesosomes possess long-standing recognition although their function remains obscure (31). Complex intracytoplasmic membrane systems have been described for specialized groups of microorganisms, which include the methaneoxidizing bacteria (6,7), the autotrophic-nitrifying bacteria (42), the photosynthetic Thiorhodaceae and Athiorhodaceae (25), the nitrogenfixing Azotobacter (28,30), Escherichia coli strain Olla (44), and Gluconobacter oxydans (2,5). Recently, intracytoplasmic membrane development in the alkane-oxidizing microorganism Acinetobacter sp.…”