Fatty Acid and Isoprenoid Quinone Composition in the classification of Bacteroides melaninogenicus and Related Taxa

Aerobic deterioration of lucerne, maize and wheat silages was characterized by rapid increases in yeast and mould flora which oxidized lactic and volatile acids resulting in increased temperature and pH. While populations of yeasts and moulds were similar, temperature increases were slightly greater for silages inoculated with Lactobacillus acidophilus and Candida spp. After 48 h the pH of the inoculated silages was higher in general and concentrations of acids were lower than controls. Bacterial growth was slight although continued lactic acid production was probable. In contrast to lucerne and maize silages, the pH of wheat silage remained stable during this period because of high butyric levels, but temperature and yeast populations increased. After 48 h the pH rose above 5 in maize and lucerne, and bacterial growth and metabolic activity resumed resulting in volatile and non-volatile acid production from carbohydrate fermentation and deamination of amino acids. During this phase of aerobic deterioration yeast growth slowed or stopped, but temperatures remained high and pH continued to climb probably because of production of ammonia. The changes in gross composition of the silages did not follow any particular pattern. Losses in dry matter were small (2.5–4.0%) and changes in individual components probably reflect this loss rather than substantial changes. Protein availability in the lucerne silages undoubtedly decreased, as protein losses were high. It is concluded that the aerobic deterioration of silage is enhanced by the addition of L. acidophilus and Candida spp. at ensiling.     

Stability of Lactic Acid Bacteria to Freezing as Related to Their Fatty Acid Composition

The viability of Streptococcus lactis and Lactobacillus sp. A-12 after freezing at -17°C for 48 h was better preserved when the cells were grown in medium supplemented with oleic acid or Tween 80 (polyoxyethylene sorbitan monooleate). A pronounced change in the cellular fatty acid composition was noted when the bacteria were grown in the presence of Tween 80. In S. lactis the ratio of unsaturated to saturated fatty acids increased from 1.18 to 2.55 and in Lactobacillus sp. A-12 it increased from 0.85 to 1.67 when Tween 80 was added to the growth medium. The antibiotic cerulenin markedly inhibited the growth of lactic acid bacteria in tomato juice (TJ) medium but had almost no effect on the growth of the bacteria in TJ medium containing Tween 80 (or oleic acid). The antibiotic inhibited markedly the incorporation of [1-¹⁴C]acetate but had no inhibitory effect on the incorporation of exogenous [1-¹⁴C]oleate (or [1-¹⁴C]palmitate) into the lipid fractions of lactic acid bacteria. Thus, the fatty acid composition of lactic acid bacteria, inhibited by the antibiotic cerulenin, can be modulated by exogenously added oleic acid (or Tween 80) without the concurrent endogenous fatty acid synthesis from acetate. The data obtained suggest that cerulenin inhibits neither cyclopropane fatty acid synthesis nor elongation of fatty acid acyl intermediates. The radioactivity of cells grown in the presence of [1-¹⁴C]oleate and cerulenin was associated mainly with cyclopropane Δ19:0, 20:0 + 20:1, and 21:0 acids. As a consequence, cerulenin caused a decrease in the ratio of unsaturated to saturated fatty acids in lactic acid bacteria as compared with cells grown in TJ medium plus Tween 80 but without cerulenin. Cerulenin caused a decrease in the viability of S. lactis and Lactobacillus sp. A-12 after freezing at -17°C for 48 h only when Tween 80 was present in the growth medium. We conclude that the sensitivity of lactic acid bacteria to damage from freezing can be correlated with specific alterations in the cellular fatty acids.     

Strand-biased Gene Distribution in Bacteria Is Related to both Horizontal Gene Transfer and Strand-biased Nucleotide Composition

Although strand-biased gene distribution(SGD) was described some two decades ago,the underlying molecular mechanisms and their relationship remain elusive.Its facets include,but are not limited to,the degree of biases,the strand-preference of genes,and the influence of background nucleotide composition variations.Using a dataset composed of 364 non-redundant bacterial genomes,we sought to illustrate our current understanding of SGD.First,when we divided the collection of bacterial genomes into non-polC and polC groups according to their possession of DnaE isoforms that correlate closely with taxonomy,the SGD of the polC group stood out more significantly than that of the non-polC group.Second,when examining horizontal gene transfer,coupled with gene functional conservation(essentiality) and expressivity(level of expression),we realized that they all contributed to SGD.Third,we further demonstrated a weaker G-dominance on the leading strand of the non-polC group but strong purine dominance(both G and A) on the leading strand of the polC group.We propose that strand-biased nucleotide composition plays a decisive role for SGD since the polC-bearing genomes are not only AT-rich but also have pronounced purine-rich leading strands,and we believe that a special mutation spectrum that leads to a strong purine asymmetry and a strong strand-biased nucleotide composition coupled with functional selections for genes and their functions are both at work.     

Lipid Composition of Tomato Leaves as Related to Plant Cold Tolerance

We studied the effects of a low nonlethal temperature (6°C) on the content and composition of polar lipids and their fatty acids in tomato (Lycopersicon esculentum Mill., cv. Sibirskie skorospelye) leaves. We demonstrated that chilling resulted in a decrease in the content of total polar lipids per 1 mg protein. The content of lipids in chloroplast membranes (monogalactosyldiacylglycerols, digalactosyldiacylglycerols, sulfoquinovosyldiacylglycerols, and phosphatidylglycerols) changed less substantially than the content of phospholipids in other cell organelles and in the cytoplasm. Neutral lipids comprised only 1% of total lipids, and their content also decreased after chilling. The relative amounts of unsaturated and saturated fatty acids in polar lipids were practically unchanged. The conclusion was drawn that the maintenance of a high level of chloroplast membrane lipids under low temperatures could play an important role in the survival of cold-tolerant plants.     

A Guide to the Natural History of Freshwater Lake Bacteria

Summary: Freshwater bacteria are at the hub of biogeochemical cycles and control water quality in lakes. Despite this, little is known about the identity and ecology of functionally significant lake bacteria. Molecular studies have identified many abundant lake bacteria, but there is a large variation in the taxonomic or phylogenetic breadths among the methods used for this exploration. Because of this, an inconsistent and overlapping naming structure has developed for freshwater bacteria, creating a significant obstacle to identifying coherent ecological traits among these groups. A discourse that unites the field is sorely needed. Here we present a new freshwater lake phylogeny constructed from all published 16S rRNA gene sequences from lake epilimnia and propose a unifying vocabulary to discuss freshwater taxa. With this new vocabulary in place, we review the current information on the ecology, ecophysiology, and distribution of lake bacteria and highlight newly identified phylotypes. In the second part of our review, we conduct meta-analyses on the compiled data, identifying distribution patterns for bacterial phylotypes among biomes and across environmental gradients in lakes. We conclude by emphasizing the role that this review can play in providing a coherent framework for future studies.     

Fatty Acid and Polar Lipid Composition in the Classification of Cellulomonas, Oerskovia and Related Taxa

Strains representing the taxa Cellulomonas, Oerskovia, Brevibacterium fermentans, Corynebacterium manihot and Nocardia cellulans were degraded by acid methanolysis and the non-hydroxylated fatty acid esters released examined by thin-layer and gas chromatography. The major fatty acid in all strains was 12-methyltetradecanoic acid ( anteiso C₁₅) which occurred together with other anteiso acids, iso and straight-chain acids. The fatty acid profiles of the cellulomonads were distinguished by the presence of 13-carbon acids and significantly higher proportions of straight-chain acids than found in the other test strains whose profiles were closely similar to one another. Two-dimensional thin-layer chromatography showed that almost identical and very characteristic polar lipid patterns were given by all the organisms under study: the only major components were diphosphatidylglycerol, phosphatidylinositol and two phospho-glycolipids chromatographing similarly to, but distinguishable from, the mono- and diacyl phosphatidylinositol dimannosides characteristic of Nocardia and other actinomycetes. The accumulated lipid data support the reclassification of B. fermentans, Cor. manihot and N. cellulans in the genus Oerskovia.     

Factors Related to the Oxygen Tolerance of Anaerobic Bacteria

The effect of atmospheric oxygen on the viability of 13 strains of anaerobic bacteria, two strains of facultative bacteria, and one aerobic organism was examined. There were great variations in oxygen tolerance among the bacteria. All facultative bacteria survived more than 72 h of exposure to atmospheric oxygen. The survival time for anaerobes ranged from less than 45 min for Peptostreptococcus anaerobius to more than 72 h for two Clostridium perfringens strains. An effort was made to relate the degree of oxygen tolerance to the activities of superoxide dismutase, catalase, and peroxidases in cell-free extracts of the bacteria. All facultative bacteria and a number of anaerobic bacteria possessed superoxide dismutase. There was a correlation between superoxide dismutase activity and oxygen tolerance, but there were notable exceptions. Polyacrylamide gel electropherograms stained for superoxide dismutase indicated that many of the anaerobic bacteria contained at least two electrophoretically distinct enzymes with superoxide dismutase activity. All facultative bacteria contained peroxidase, whereas none of the anaerobic bacteria possessed measurable amounts of this enzyme. Catalase activity was variable among the bacteria and showed no relationship to oxygen tolerance. The ability of the bacteria to reduce oxygen was also examined and related to enzyme content and oxygen tolerance. In general, organisms that survived for relatively long periods of time in the presence of oxygen but demonstrated little superoxide dismutase activity reduced little oxygen. The effects of medium composition and conditions of growth were examined for their influence on the level of the three enzymes. Bacteria grown on the surface of an enriched blood agar medium generally had more enzyme activity than bacteria grown in a liquid medium. The data indicate that superoxide dismutase activity and oxygen reduction rates are important determinants related to the tolerance of anaerobic bacteria to oxygen.     

Differentiation of Gram-Negative, Nonfermentative Bacteria Isolated from Biofilters on the Basis of Fatty Acid Composition, Quinone System, and Physiological Reaction Profiles

Gram-negative, nonfermentative bacteria isolated from biofilters for off-gas treatment of animal-rendering-plant emissions were differentiated by whole-cell fatty acid analysis, quinone analysis, and numerical taxonomy based on their physiological reaction profiles. The last system consisted of 60 physiological tests and was arranged as a microtest system on microtitration plates. Based on fatty acid analyses, 31 isolates were separated into six clusters and five single-member clusters. The isolates of two clusters were identified as Alcaligenes faecalis and Pseudomonas diminuta. The remaining nine clusters were characterized by their fatty acid profiles, quinone systems, and physiological reaction profiles. Clusters resulting from fatty acid analyses were compared with those resulting from physiological reaction profiles. Six clusters could be confirmed this way. The efficiency of the physiological test system was increased by the prearrangement of the isolates according to their quinone type.     

The Variation in Staining Character of Bacteria as Related to the Reserve Food Material Within the Organism

When Bacillus cereus is starved it tends to lose Gram-positivity at 37° C., the not at ice box temperature. In the latter case the cells are probably dormant undergoing no significant change, but the results in the former case are thought to be due to the using up of acidic reserve food materials (nucleins, nucleo-proteins, etc.) when the organism grows in the absence of a nutritive environment.     

Intervarietal Differences in the Amino Acid Composition of Pea Roots as Related to their Response to Salinity

The salt tolerance of three cultivars of Pisum sativum L. asdefined by root growth on saline substrate was in the orderDan > Alaska > Laxton Progress. The total content of freeamino acids decreased in Alaska, but not in Laxton Progress,with increasing salinity, while the content of the free basicamino acids increased with salinity. In both cultivars salinityinduced accumulation of free proline, but not enough to maintainthe osmotic adaptation of the cytoplasm. Proline accumulationcould not account for the greater tolerance of the Alaska cultivar.Both cultivars contain large amounts of glutamic acid and homoserine.The amino acid composition of protein of the Alaska cultivaris affected much more by salinity than is that of Laxton Progress.In Alaska salinity induces an increase in aspartic and glutamicacids, threonine, serine, leucine and isoleucine. The totalcontent of basic amino acids decreases with salinity. The proteinof Laxton Progress is very rich in leucine and its amount slightlydecreases with salinity. In the most tolerant cultivar, Dan,there is more proline in the protein than in the other two cultivarsand its content of leucine increases with salinity. The onlyfeatures which show some correlation with salinity toleranceare proline content (Dan > Alaska > Laxton Progress) andan increase in leucine content in the protein, with increasingsalinity. Pisum sativum L, pea, amino acid composition of roots, salinity