Effects of random motility on growth of bacterial populations

A spatially distributed mathematical model is developed to elucidate the effects of chemical diffusion and cell motility as well as cell growth, death, and substrate uptake on steady-state bacterial population growth in a finite, one-dimensional, nonmixed region. The situation considered is growth limited by a diffusing substrate from an adjacent phase not accessible to the bacteria. Chemotactic movement is not considered in this paper; we consider only randomwalk-type random motility behavior here. The following important general concepts are suggested by the results of our theoretical analysis: (a) The significance of random motility effects depends on the magnitude of the ratio/kL ², where is the bacterial random motility coefficient,k is the growth rate constant, andL is the linear dimension of the confined growth region. (b) In steady-state growth in a confined region, the bacterial population size decreases as increases. (c) The effect of on population size can be great; in fact, sometimes relative population sizes of two species can be governed primarily by the relative values of rather than by the relative values ofk.     

Occurrence and expression of β-galactosidase in dextran-producing Leuconostoc species

The occurrence and expression of -galactosidase among various dextran-producing Leuconostoc strains was determined. -Galactosidase was detected from four of twelve Leuconostoc strains tested. -Galactosidase in L. mesenteroides was induced by lactose and was repressed by glucose. Growth curves of L. mesenteroides on lactose indicated extended lag and late growth phases that were shortened when the inoculum was preexposed to lactose.     

Plant growth regulatory metabolites from novel actinomycetes

Metabolites from 796 isolates of aerobic actinomycetes were screened for plant growth regulatory properties using an algal bioassay. These included 266 isolates ofStreptomyces, 28 unidentified actinomycetes, and 502 isolates of novel actinomycetes represented by 18 genera. Algal growth inhibition of 30% was observed with 60 isolates, 37 of which belonged to the genusStreptomyces. Among other inhibitors were 8 isolates ofActinomadura, 6 ofActinoplanes, 2 each of the generaThermomonospora, Streptoverticillium, andPromicromonospora, and 3 unidentified. Metabolites from 70 isolates promoted algal growth by 20%. These included 13 isolates ofMicromonospora, 11 ofStreptomyces, 6 ofNocardia, 5 ofActinomadura, and 4 each ofRhodococcus andThermomonospora. Sixteen unidentified isolates; 3 isolates ofPromicromonospora; 2 isolates each ofActinoplanes, Streptosporangium, andOerskovia; and 1 of Thermoactinomyces peptonophilus-like organism andSaccharomonospora viridis also promoted the algal growth by 20%. The plant growth inhibitory properties of 9 actinomycetes and the growth promoting properties of 6 were demonstrable during the secondary screening on higher plants using chemicals extracted from the culture broth. The metabolites fromMicromonospora, Nocardia, Rhodococcus, Streptosporangium, andOerskovia isolates were associated with plant growth promotion only; those fromStreptomyces were most frequently involved with the growth inhibition.This is Michigan Agriculture Experiment Station Journal Article No. 12191.     

Sequence Analysis of Leuconostoc mesenteroides Bacteriophage Φ1-A4 Isolated from an Industrial Vegetable Fermentation

Vegetable fermentations rely on the proper succession of a variety of lactic acid bacteria (LAB). Leuconostoc mesenteroides initiates fermentation. As fermentation proceeds, L. mesenteroides dies off and other LAB complete the fermentation. Phages infecting L. mesenteroides may significantly influence the die-off of L. mesenteroides. However, no L. mesenteroides phages have been previously genetically characterized. Knowledge of more phage genome sequences may provide new insights into phage genomics, phage evolution, and phage-host interactions. We have determined the complete genome sequence of L. mesenteroides phage Φ1-A4, isolated from an industrial sauerkraut fermentation. The phage possesses a linear, double-stranded DNA genome consisting of 29,508 bp with a G+C content of 36%. Fifty open reading frames (ORFs) were predicted. Putative functions were assigned to 26 ORFs (52%), including 5 ORFs of structural proteins. The phage genome was modularly organized, containing DNA replication, DNA-packaging, head and tail morphogenesis, cell lysis, and DNA regulation/modification modules. In silico analyses showed that Φ1-A4 is a unique lytic phage with a large-scale genome inversion (∼30% of the genome). The genome inversion encompassed the lysis module, part of the structural protein module, and a cos site. The endolysin gene was flanked by two holin genes. The tail morphogenesis module was interspersed with cell lysis genes and other genes with unknown functions. The predicted amino acid sequences of the phage proteins showed little similarity to other phages, but functional analyses showed that Φ1-A4 clusters with several Lactococcus phages. To our knowledge, Φ1-A4 is the first genetically characterized L. mesenteroides phage.Bacteriophages are the most abundant biological entities (estimated to be on the order of ≥10³¹) on the planet (9, 18). Phages are ubiquitous in nature and can influence the microbial ecology and genetics of bacteria. Because of their small (usually <60 kb) genomes, phages can provide an excellent model system for studying many biological processes, including DNA replication and genetic evolution. Despite this, many phages remain uncharacterized. Very little is known about phage diversity and phage-host interactions owing to the small number of sequenced phages. Furthermore, the existing phage sequence database is highly biased toward a limited spectrum of phage hosts, namely, Enterobacteriaceae, Bacillus, Staphylococcus, Pseudomonas, Vibrio cholerae, Lactococcus, Streptococcus thermophilus, and S. pyogenes. The majority of host species for sequenced phages are either pathogenic or dairy-related bacteria. Most of the newly sequenced phage genes have no assigned functions or matches in the GenBank database (7).Vegetable fermentations rely on a variety of lactic acid bacteria (LAB). The proper succession of LAB directly determines the quality and safety of the final fermentation products. Leuconostoc mesenteroides initiates most vegetable fermentations. It converts the sugars in vegetables (primarily glucose and fructose) to lactic acid, acetic acid, ethanol, CO₂, and other flavor compounds (22, 58, 59, 60, 61). Acid production lowers the pH of fermenting vegetables and inhibits the growth of many microorganisms, including pathogens. CO₂ production promotes the establishment of an anaerobic environment which favors the growth of other LAB. The metabolites produced by L. mesenteroides largely determine the flavor characteristics of the final products. As fermentation proceeds, L. mesenteroides rapidly dies off. Other LAB, including Lactobacillus plantarum, take over and complete the fermentation.It has been a widely held view that the disappearance of L. mesenteroides and the subsequent bacterial succession in sauerkraut fermentations are due to the inhibitory effect of acids that accumulate during fermentation (54, 61). Little is known about other factors that may play a role in bacterial succession. Recent studies have shown that phages are present in the vegetable fermentations (4, 47, 48, 74, 75). Because of the rapid lytic cycle of these phages, they may significantly impact starter cultures and bacterial succession in vegetable fermentations (56). Phages active against L. mesenteroides have been isolated and characterized (48); however, genome sequences have not been reported.L. mesenteroides phage 1-A4 (designated Φ1-A4) is of particular interest. Φ1-A4 is a lytic phage that was repeatedly isolated during the initial stages of a commercial sauerkraut fermentation. As a result, Φ1-A4 may significantly influence the survival of L. mesenteroides and flavor development during sauerkraut fermentation. It was found that Φ1-A4 infects at least three different strains of L. mesenteroides (48), and therefore it may also promote genetic exchange and genetic diversity in microbial communities (34).The objectives of this study were to determine and analyze the complete genome sequence of Φ1-A4, to experimentally identify the structural protein genes, and to compare the genome organization with that of related phages. To our knowledge, this study represents the first complete genomic and molecular characterization of Leuconostoc phage. The results from this study may provide new insights into our understanding of phage genetics. This study may aid the development of phage control technologies in vegetable and other fermentations that are susceptible to phage attack.     

Interactions between freshwater bacteria andAnkistrodesmus braunii in batch and continuous culture

Batch and continuous cultures ofAnkistrodesmus braunii were established in an inorganic medium with growth rate limited by P. In batch culture, inoculation of lake water bacterial isolates ofPseudomonas sp. andFlavobacterium sp. showed that thePseudomonas isolate was capable of more rapid growth on algal exudates of lytic products than was theFlavobacterium isolate. When inoculated singly into a continuous culture (D=0.267 day^–1; P level, 2M), theFlavobacterium isolate initially caused a decrease in the population density of the alga, but then steady states for both organisms were obtained. ThePseudomonas isolate under the same conditions caused a rapid washout of the algal culture, and steady-state conditions were never obtained. When thePseudomonas isolate was added to the two-member, steady-state system ofA. braunii andFlavobacterium, the algal population again washed out of the vessel, followed by theFlavobacterium and then thePseudomonas isolate. A transient increase in the P concentration to 200M in the culture vessel caused the low algal population level to increase, followed by increases in the bacterial isolates when the algal population was high enough to supply the required organic carbon source. The system demonstrated that competition for P between the alga and the bacteria can occur, and the results were dependent on the algal and bacterial relative growth rates. The bacterial growth rates were limited initially by organic substrates produced by the alga, and the different bacterial isolates competed for these substrates.     

XE-1019: Plant response,translocation, and metabolism

XE-1019 [(E)-1-(4-chlorophenyl)-4,4,-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol] was injected into bean plants (Phaseolus vulgaris L. Black Valentine) at doses of 0.1–1000 g/plant and caused reduced height growth, fresh weight, and leaf area 7 days after treatment. The sprout growth of California privet (Ligustrium ovalifolium Hassk.) was inhibited 52% by 10 g and growth was further suppressed as the dose was increased to 100 g, without injury. The shoot growth of American sycamore (Platanus occidentalis L.) and yellow-poplar (Liriodendron tulipifera L.) was progressively inhibited after 3 months as the injected dose of XE-1019 was increased from 2.5 to 240 mg/tree. Neither species was injured. Growth of 1-year-old trees of Golden Delicious apple (Malus domestica Borkh) was inhibited 28 days after injecting the stem with 2 mg of¹⁴C-labeled XE-1019. At this time, 2% of¹⁴C activity has been translocated into the new shoots and 3% was present in the xylem and phloem of the scion. From 96 to 99% of¹⁴C-activity found in the xylem and phloem and 92% in the new shoot tissue chromatographed with XE-1019. This indicates that little degradation of XE-1019 occurred during the initial inhibition period.     

Comparison of the effect of antibiotic substances on sclerotia of Mycosphaerella ligulicola and Colletotrichum coccodes

Summary Sclerotia ofColletotrichum coccodes tolerated much higher concentrations of actidione in agar than did sclerotia ofMycosphaerella ligulicola. With increase in concentration of the antibiotic sclerotia of both species took longer to germinate. Increased resistance of both species to actidione developed after growth of a single generation on media containing the antibiotic. Sclerotia ofC. coccodes survived 5 days immersion in a bacterial culture filtrate whereas scleroia ofM. ligulicola ceased to be viable after a similar period.Sclerotia ofC. coccodes andM. ligulicola exhibited strand and loose types of formation respectively. The degree of resistance of these sclerotia to antibiotic substances was correlated with both longevity in soil and type of formation, but, in general, there is unlikely to be a relationship between structure of the sclerotium and longevity.     

Infection of transformable cells ofHaemophilus influenzae by bacteriophage and bacteriophage DNA

Summary A phage HP1, infecting transformable cells ofHaemophilus influenzae Rd, has been isolated. The general properties of the wild type and of a clear plaquemutantc1 employed for most of the experiments are described. Phage DNA is infective for transformableHaemophilus cells with an efficiency (plaqueforming units of the original phage recovered as DNA-infected cells) of up to 6×10^–3. The competence ofHaemophilus cells for infection with phage DNA parallels the competence for transformation with bacterial DNA.Both HP1 and thec1 mutant are able to lysogenize their host, and the lysogenic cells are readily induced by UV. Competent non-lysogenicHaemophilus cells can be infected by DNA of lysogenic cells, thereby giving rise to phage progeny. Thus, the phage genetic material can be introduced into competentHaemophilus cells in three different ways: injection from intact phage, and infection with either phage DNA or with bacterial DNA carrying the prophage.The UV inactivation curves for infectious phage DNA and for complete phages are similar, both indicating the occurrance of host-cell reactivation. Photoreactivationin vitro of infectious phage DNA takes place to about the same high extent as observed with bacterial transforming DNA.The usefulness of this system for investigating bacterial transformation and biological effects ofin vitro treatment of DNA is discussed.with the technical assistance ofSandra J. Antoine With 4 Figures in the TextPreliminary report presented at the 7th Annual Bacterial Transformation Meeting, Aspen, Colorado, June 17–19, 1963.Supported by a travel grant from the Deutsche Forschungsgemeinschaft.Supported by Research Carreer Development Award GM-K3-7500 and Research Grant RH 00221 from the U.S. Public Health Service.     

Peristance of bacteria in the presence of viable,nonencysting, bacterivorous ciliates

Laboratory studies of the interactions between a bacterial population and a population of bacterivorous ciliates consistently show that the bacteria are able to persist in the presence of viable ciliates. Reproduction of the bacteria, presumably at the expense of substrates produced by death and lysis of the ciliates and/or by their metabolic activity, has been suggested to be a factor involved in the observed bacterial persistence. Rates and extents of growth ofEscherichia coli in broths of mixed cultures of this bacterium and the ciliateTetrahymena pyriformis were determined in order to provide some data necessary to assess the importance of the suggested factor. In addition, an attempt was made to suppress bacterial growth on produced substrates so that feeding of the ciliates could be studied free of this complication. However, the procedure tested—addition of the antibiotic chloramphenicol (CM) at a concentration of 150g/ml—led to other complications that made it impossible to obtain the desired information about feeding.     

Studies on Baker's yeasts of East Pakistan II

Summary 88 strains of yeast and 4 strains of fungi imperfecti have been isolated from dough from three more districts of East Pakistan. The yeasts comprise 53 strains ofSaccharomyces carlsbergensis, 15 strains ofCandida krusei, 8 strains ofCandida guilliermondii var.membranaefaciens, 6 strains ofTorulopsis colliculosa, 2 strains ofTorulopsis globosa, and 4 strains ofHansenula anomala. Of the four strains of fungi imperfecti, 3 belonged toCladosporium butyri and one toSporophora sp. TheSporophora sp. is considered to be a contaminant.The 92 isolates have been tested for their capacity to ferment -methyl glucoside. The possibility of the utilisation of the fermentation of -methyl glucoside as an additional character in yeast taxonomy has been discussed.Tests for the syntheses of various members of vitamin B-complex have shown that all the 92 isolates are more or less autotrophic.     

Inhibition-threshold substrate concentrations

A proposed substrate inhibition model (M. C. Tseng and M. Wayman, Can. J. Microbiol., 21 , 994 (1975)), ((1)) ((2)) derived from yeast growth rates has been applied to data for bacterial growth: Pseudomonas methanica grown on methanol and Arthrobacter AK19 grown on n-butanol. The model represents the experimental data very well.     

Effect of different carbon and nitrogen sources on the growth and sporulation of Claviceps microcephal (Wallr) TUL.

The effect of different carbon and nitrogen compounds on growth and sporulation ofC. microcephala (Wallr.)Tul. causing ergot disease of Bajra has been studied. Nine different sources of carbon were used but cane sugar was found to be the best source for both, growth and sportulation of the fungus. Glucose, sucrose and maltose gave good growth but fair sporulation. Lactose and sorbitaol proved to be the poor sources. However, fungus failed to utilize starch, dextrin and mannitol.Nineteen nitrogen compounds were tried for the growth and sporulation of the fungus. Best growth and sporulation were supported by peptone and glycine. L-asparagine, DL-valine, Urea, magnesium nitrate and L-proline supported good growth and fair sporulation except DL-valine where it was excellent. Poor growth was obtained on L-isoleucin, ammonium sulphate, potassium nitrate,-alanine, ammonium chloride, DL-aspartic acid and DL-methionine. Fungus failed to utilize thio-urea.     

Leaf isotopic (δ<Superscript>13</Superscript>C and δ<Superscript>15</Superscript>N) and nitrogen contents of<Emphasis Type="Italic"> Carex</Emphasis> plants along the Eurasian Coastal Arctic: results from the Northeast Passage expedition

We conducted surrogate in-situ physiological performance measures (¹³C and ¹⁵N) of Carex plants from 15 Eurasian Coastal Arctic sites. Leaf carbon isotope discrimination (LCID) of Carex plants exhibited significant differences between sites (populations). Additionally, LCID was inversely correlated with mean annual temperature and stomatal density, and to a lesser extent, with the depth of thaw. Leaf ¹⁵N values of Carex plants exhibited significant differences between sites without differences among ramet age classes, and the leaf ¹⁵N values were inversely correlated with mean annual precipitation. These ranges of Carex leaf gas exchange and mineral nutrition across the Eurasian Arctic may contribute to Carexs dominance in coastal tundra systems. Also, the inverse correlation between LCID, precipitation, and temperature indicates that, as precipitation increases and temperatures continue to warm in Eurasia, leaf gas exchange may actually be lower in the future, leading to reductions in shoot growth and lower above-ground biomass production.     

Competitive colonization betweenPseudomonas species in sterile soils

When introduced as pairs into irradiated, sterile soils, aPseudomonas fluorescens strain prevented optimal colonization by aP. putida strain. The addition ofP. putida to sterile soil already populated byP. fluorescens impeded growth ofP. putida in that soil. However, addingP. fluorescens to soil populated withR. putida did not prevent growth ofP. fluorescens and caused a decrease in the titer ofP. putida. This preemptive colonization/exclusion phenomenon was also observed between two isogenic strains. The degree of exclusion depended on the amount of time between the inoculation of the two strains and which organism was introduced first. These results suggest competition for similar niches in soils and a hierarchy of fitness among pseudomonads sharing a soil environment. Autoclaving of the soil removed the competitive colonization betweenPseudomonas spp. observed in irradiated soils. The competitive colonization of irradiated soils by these twoPseudomonas sp. was reflected in their relative survival when introduced into nonsterile soil.     

Comparison of α-acetolactate synthase and α-acetolactate decarboxylase in Lactococcus spp. and Leuconostoc spp.

Summary Cell-free extracts of Leuconostoc and Lactococcus species were tested for their -acetolactate synthase and -acetolactate decarboxylase activities. In Leuconostoc mesenteroides subsp. cremoris, Leuconostoc mesenteroides subsp. mesenteroides and Leuconostoc lactis, the Km of -acetolactate synthase for pyruvate was close to 10 mM whereas it was 30 mM in Lactococcus lactis subsp. lactis biovar. diacetylactis. The Km of -acetolactate decarboxylase for -acetolactic acid was very low (0.3 mM) in Leuconostoc species in comparison to Lactococcus lactis subsp. lactis biovar. diacetylactis (60 mM). In the latter bacterium, -acetolactate decarboxylase showed a sigmoidal dependance upon -acetolactic acid and was activated by the three branchedchain amino acids: leucine, isoleucine and valine.     

Characterization of the EstP Protein in Drosophila melanogaster and Its Conservation in Drosophilids

The -esterase cluster of D. melanogaster comprises two tandemly duplicated genes. Est6 encodes the well-characterized 5 gene, but the product of the second gene, denoted EstP, had not previously been identified. Here we show that the EstP gene encodes the carboxylesterase EST7. Expression of EstP using the Baculovirus system led to production of a carboxylesterase biochemically indistinguishable from EST7. Furthermore, a naturally occurring EstP variant produces greatly reduced amounts of EstP mRNA and no detectable EST7 protein. Finally, introduction of a wild-type copy of EstP by germline transformation into the variant strain confers the wild-type EST7 phenotype. We show that EST7 differs from EST6 in its substrate and inhibitor specificities and tissue distribution. Germline transformation experiments show that EstP expression is controlled by sequences located between 192 bp 5 and 609 bp 3 of the EstP coding region. Data comparisons with other drosophilid esterases suggest that the site of expression, and hence the function, of EST7 has been conserved across lineages in both the subgenera Drosophila and Sophophora.     

Unusual bloom of star-like prosthecate bacteria and filaments as a consequence of grazing pressure

In seawater used for shrimp aquaculture in French Polynesia, the grazing of small bacteria (rods and coccoids) allowed the growth ofAncalomicrobium cells (to more than 2×10⁶ cells ml^–1) and large filaments > 10m in length (5×10⁶ cells ml^–1). Their contribution to the increase in total bacterial number after grazing was 27.8 and 9.8%, respectively. These large bacteria are not grazed on by microflagellates, but are available for mesoplankton larvae.     

Survival of ciliate protozoa under starvation conditions and at low bacterial levels

Under starvation conditions, 50% survivorship times displayed no significant relationship with cell size in 2 ciliate species in this study and 5 protozoan species from the literature. Differences in survival ability were attributed to differences in weight-specific respiratory rate and relative motility among these 7 species. At low bacterial levels, 4 ciliate species in this study displayed significant differences in survivorship. High survivorship ofEuplotes patella relative to that ofParamecium caudatum andParaurostyla sp. at low ciliate densities was attributed to the lower individual energy requirements of this smaller species. High survivorship ofStentor coeruleus was interpreted as an effect of its large quantity of reserves and low respiratory rate. The survivorship ofE. patella was reduced at a higher population density. Four ciliate species survived longer at 15C than at 22C. Q₁₀ values based on 50% survivorship times at these 2 temperatures were much lower than Q₁₀ values based on respiratory rates and growth rates of well-fed ciliates over a similar temperature range.     

A study of the nutritional requirements of a selectedHaemophilus ducreyi strain by impedance and conventional methods

The growth and nutritional requirements ofHaemophilus ducreyi (CIP 542^T) were determined in liquid media by impedance technology. We found thatH. ducreyi grew in a liquid mixture of Proteose Peptone No. 3, hemin,l-serine, glucose,l-glutamine, and inorganic salts. The peptone in the medium was essential forH. ducreyi growth, and the growth factor (or factors) in the peptone was stable to autoclaving (15 min, 121°C) and could not be extracted with organic solvents (21 chloroform/methanol) from either acidic (1N CH₃COOH), neutral (pH 7.1), or basic (1N NaOH) solutions. Hemin was also an essential component for the growth ofH. ducreyi, but a much lower concentration of hemin (5.0 g/ml) was required than has been previously reported in the literature (25 g/ml). Using impedance technology to measureH. ducreyi doubling times, we showed that bovine albumin enhancesH. ducreyi growth.     

Is the lactose-utilization ability ofRhizobium ofSesbania procumbens a vestigeal function?

Rhizobium SBS-R100, isolated from the stem nodules ofSesbania procumbens, synthesized -galactosidase constitutively. Transposon mutagenesis by Tn9 induced mutants defective in lactose utilization; the mutations did not interfere with growth, nodulation or N₂ fixation. Mouse monoclonal antibody raised against -galactosidase ofEscherichia coli reacted with soluble proteins of wild typeRhizobium SBS-R100. Anin vivo constructed recombinant plasmid pSBS-4 complemented aRhizobium mutant defective in lactose utilization.