The adaptation of Bact. coli mutabile to lactose

1954 ◽  
Vol 223 (1154) ◽  
pp. 420-420
Keyword(s):  
Inoculum Size ◽  
Colony Development ◽  
Lag Phase ◽  
Normal Cells ◽  
Adaptive Process ◽  
Large Numbers ◽  
Parent Culture ◽  
Mutation Theory ◽  
Special Circumstances ◽  
New Evidence

When Bact. coli mutabile not previously exposed to lactose is plated on lactose-ammonium sulphate agar the number of normal-sized colonies (lac + ) eventually formed is a complicated function of the inoculum size. For small numbers all the cells plated eventually form colonies; for large numbers the colony yield is determined not by a number of mutants in the parent culture but by plate exhaustion (for which the earlier developing colonies are chiefly responsible). The time of appearance of the lac + colonies is much longer than with a culture previously grown in lactose. Thus lac + mutants could not have been present from the start unless their growth is inhibited by an excess of normal cells. When, however, a small number of previously adapted cells are mixed with an excess of unadapted cells the presence of the latter does not impede the development on agar of lac + colonies from the former. When cells are first placed in a liquid lactose medium and samples are transferred at intervals during the ensuing lag phase, the time needed for colony development on lactose-agar progressively diminishes, once again showing that an adaptive process is occurring during the lag in the liquid medium. In certain special circumstances the adaptation to the liquid lactose medium may occur with abnormal speed. The growth rate of newly adapted strains is at first variable. If interpreted by a mutation theory the observations would demand the assumption of a complex polygenetic system for which current applications of the Luria-Delbrück and Lea-Coulson theories would be invalid. Recent arguments about the mutational nature of these phenomena are criticized in the light of the new evidence.

The adaptation of Bact . coli mutabile to lactose

1954 ◽  
Vol 142 (907) ◽  
pp. 225-241 ◽  
Keyword(s):  
Inoculum Size ◽  
Colony Development ◽  
Lag Phase ◽  
Normal Cells ◽  
Adaptive Process ◽  
Large Numbers ◽  
Parent Culture ◽  
Mutation Theory ◽  
Special Circumstances ◽  
New Evidence

When Bact . coli mutabile not previously exposed to lactose is plated on lactose-ammonium sulphate agar the number of normal sized colonies (lac + ) eventually formed is a complicated function of the inoculum size. For small numbers all the cells plated eventually form colonies; for large numbers the colony yield is determined not by a number of mutants in the parent culture but by plate exhaustion (for which the earlier developing colonies are chiefly responsible). The time of appearance of the lac + colonies is much longer than with a culture previously grown in lactose. Thus lac + mutants could not have been present from the start unless their growth is inhibited by an excess of normal cells. When, however, a small number of previously adapted cells are mixed with an excess of unadapted cells the presence of the latter does not impede the development on agar of lac + colonies from the former. When cells are first placed in a liquid lactose medium and samples are transferred at intervals during the ensuing lag phase, the time needed for colony development on lactoseagar progressively diminishes, once again showing that an adaptive process is occurring during the lag in the liquid medium. In certain special circumstances the adaptation to the liquid lactose medium may occur with abnormal speed. The growth rate of newly-adapted strains is at first variable. If interpreted by a mutation theory the observations would demand the assumption of a complex polygenetic system for which current applications of the Luria-Delbrück and Lea-Coulson theories would be invalid. Recent arguments about the mutational nature of these phenomena are criticized in the light of the new evidence.

scholarly journals ADAPTATION OF MASTITIS STREPTOCOCCI TO MILK

1929 ◽  
Vol 50 (3) ◽  
pp. 279-291 ◽  
Author(s):  
F. S. Jones ◽  
H. S. Simms
Keyword(s):  
Lag Phase ◽  
Large Numbers

The data here presented indicate that the inhibitory principle affecting the growth of streptococci in milk is not greatly utilized during the lag phase and that the abrupt termination of lag is not due to the utilization of the principle. They further indicate that the sudden beginning of growth cannot be ascribed to a resistant type of streptococcus present in the culture from the first, but to an adaptation occurring during the lag phase. The addition of large numbers of dead or living streptococci to milk, for limited periods, fails to diminish appreciably the inhibitory principle.

Questions Raised in Excavating the Recent Dead

2016 ◽  
Author(s):  
Sian Anthony
Keyword(s):  
Twentieth Century ◽  
Material Culture ◽  
Working Life ◽  
North West ◽  
The North ◽  
Large Numbers ◽  
Short Period ◽  
Special Circumstances ◽  
Historic Cemetery ◽  
Large Sections

The decision to excavate a modern cemetery in the heart of Copenhagen prompted questions which revealed how the sensitive borderlines surrounding the recent dead are dealt with by archaeologists. When the plans for a new metro line were revealed in Copenhagen, the location of one station within a historic cemetery was controversial. Assistens cemetery is an early example of a landscape, or garden, cemetery (Rugg 1998; Tarlow 2000), designed and ordered according to fashionable contemporary garden principles and aesthetics. It has remained a much-loved place where famous personalities are buried as well as many ordinary citizens of Copenhagen. Although burial within the cemetery has become increasingly rare, it is still in occasional use for new interments and for gardens of remembrance for the burial and disposal of ashes. However, in the 1980s changing municipal plans for the cemetery re-designated large sections of it as a park, as described in Helweg and Linnée Nielsen (2010). This change of status enabled the Copenhagen metro company (Metroselskabet) to consider the placement of a station in one corner of the cemetery. Excavation of this site from 2009 to 2011 resulted in the archaeological recording of the material culture of the cemetery including around one thousand burials, their grave-pits, funerary material culture, and some aspects of the working life of the cemetery (Anthony et al. 2016). Assistens cemetery was originally created in 1760 and later expanded in 1805/6. The excavation focused on the north-west corner of the 1805/6 extension, an area surrounding a cemetery administration building (graverbolig). The area was filled by the mid-nineteenth century and continued to be used intensively for the next hundred years. In the latter part of the twentieth century, coffin burial became less frequent but continued until the 1980s. The occasional placement of cremation urns began in the early twentieth century and continued in large numbers into the 1990s (Helweg and Linnée Nielsen 2010). Burial is now uncommon in the entire cemetery and only takes place in special circumstances. In contrast to UK cemetery regulations, Danish law allows for graves to be removed after only twenty years, so there is the possibility of reusing grave plots after this short period by removing the previous coffins.

Dreaming and Waking Thought as a Reflection of Memory Consolidation

2018 ◽  
Author(s):  
Erin J. Wamsley
Keyword(s):  
Memory Consolidation ◽  
Semantic Information ◽  
Memory Systems ◽  
Remote Memory ◽  
Alternative View ◽  
Adaptive Process ◽  
Spontaneous Thought ◽  
New Evidence

Dreaming has often been viewed as a “mysterious” experience entirely distinct from waking cognition. An alternative view proposes that dreams are generated by the same fundamental processes that give rise to spontaneous thought during wakefulness. New evidence suggests that these processes include activity of the brain’s memory systems, supporting consolidation of newly encoded experience. During both sleep and wakefulness, fragments of recently encoded memory are recombined with related remote memory and semantic information to create novel scenarios. This is an adaptive process that contributes to the “consolidation” of memory and is reflected in the phenomenology of both our nightly dreams and waking daydreams.

scholarly journals The use of N-methylprotoporphyrin dimethyl ester to inhibit ferrochelatase in Rhodopseudomonas sphaeroides and its effect in promoting biosynthesis of magnesium tetrapyrroles

1982 ◽  
Vol 208 (2) ◽  
pp. 479-486 ◽  
Author(s):  
J D Houghton ◽  
C L Honeybourne ◽  
K M Smith ◽  
H D Tabba ◽  
O T G Jones
Keyword(s):  
Dimethyl Ester ◽  
Cell Suspensions ◽  
Maximum Effect ◽  
Lag Phase ◽  
Rhodopseudomonas Sphaeroides ◽  
Normal Cells ◽  
Low Concentrations ◽  
Cytochrome Content ◽  
Monomethyl Ester ◽  
Substrate Addition

N-Methylprotoporphyrin dimethyl ester inhibits ferrochelatase in isolated membranes of Rhodopseudomonas sphaeroides at low concentrations (around 10 nm). Full inhibition developed after a short lag phase. The inhibition was non-competitive with porphyrin substrate. Addition of inhibitor to growing cultures of Rps. sphaeroides caused a decrease (near 40%) in cytochrome content and a severe inhibition of ferrochelatase; the excretion of haem into the medium by cell suspensions was also severely inhibited. The addition of N-methylprotoporphyrin dimethyl ester to suspensions of photosynthetically competent Rps. sphaeroides Ga caused excretion of Mg-protoporphyrin monomethyl ester. When added to mutants V3 and O1, magnesium divinylphaeoporphyrin a5 monomethyl ester and 2-devinyl-2-hydroxyethylphaeophorbide a were excreted, with maximum effect at around 3 microM-inhibitor in the medium. The results are interpreted to suggest that the inhibitor decreases concentration of intracellular haem, which normally controls the activity of 5-aminolaevulinate synthetase. Unregulated activity of this enzyme leads to overproduction of protoporphyrin, which is diverted to the bacteriochlorophyll pathway. Further control operates at magnesium protoporphyrin ester conversion in normal cells.

Autophagy is associated with apoptosis in cisplatin injury to renal tubular epithelial cells

2008 ◽  
Vol 294 (4) ◽  
pp. F777-F787 ◽  
Author(s):  
Cheng Yang ◽  
Varsha Kaushal ◽  
Sudhir V. Shah ◽  
Gur P. Kaushal
Keyword(s):  
Cell Death ◽  
Epithelial Cells ◽  
Beclin 1 ◽  
Lag Phase ◽  
Tubular Epithelial Cells ◽  
Renal Tubular Epithelial Cells ◽  
Normal Cells ◽  
Life And Death ◽  
Renal Tubular ◽  
Induced Apoptosis

Autophagy has emerged as another major “programmed” mechanism to control life and death much like “programmed cell death” is for apoptosis in eukaryotes. We examined the expression of autophagic proteins and formation of autophagosomes during progression of cisplatin injury to renal tubular epithelial cells (RTEC). Autophagy was detected as early as 2–4 h after cisplatin exposure as indicated by induction of LC3-I, conversion of LC3-I to LC3-II protein, and upregulation of Beclin 1 and Atg5, essential markers of autophagy. The appearance of cisplatin-induced punctated staining of autophagosome-associated LC3-II upon GFP-LC3 transfection in RTEC provided further evidence for autophagy. The autophagy inhibitor 3-methyladenine blocked punctated staining of autophagosomes. The staining of normal cells with acridine orange displayed green fluorescence with cytoplasmic and nuclear components in normal cells but displayed considerable red fluorescence in cisplatin-treated cells, suggesting formation of numerous acidic autophagolysosomal vacuoles. Autophagy inhibitors LY294002 or 3-methyladenine or wortmannin inhibited the formation of autophagosomes but induced apoptosis after 2–4 h of cisplatin treatment as indicated by caspase-3/7 and -6 activation, nuclear fragmentation, and cell death. This switch from autophagy to apoptosis by autophagic inhibitors further suggests that the preapoptotic lag phase after treatment with cisplatin is mediated by autophagy. At later stages of cisplatin injury, apoptosis was also found to be associated with autophagy, as autophagic inhibitors and inactivation of autophagy proteins Beclin 1 and Atg5 enhanced activation of caspases and apoptosis. Our results demonstrate that induction of autophagy mounts an adaptive response, suppresses cisplatin-induced apoptosis, and prolongs survival of RTEC.

scholarly journals A physico-chemical study of some induced changes in the morphology of Bacterium lactis aerogenes . A theory of the balance and adaptive variation of certain enzyme processes in bacteria

1944 ◽  
Vol 132 (866) ◽  
pp. 47-67 ◽  
Keyword(s):  
Ammonium Sulphate ◽  
Glucose Concentration ◽  
Normal Growth ◽  
Chemical Study ◽  
Growth Cycle ◽  
Enzyme Synthesis ◽  
Inoculum Size ◽  
Lag Phase ◽  
Good Representation ◽  
Independent Events

A strain of Bacterium lactis aerogenes giving normal growth when inoculated from bouillon into a standard glucose-phosphate-ammonium sulphate medium yields many long snake-like forms when inoculated into a similar medium with a much lower glucose concentration. The size distribution in the cultures giving the snake-forms is quite different from normal, and is represented by the equation n l = n exp ( — l/l̄ ), where n l is the number of cells of length greater than l, n is the total number and l̄ is the mean length. This holds well over most of the range but does not take into account an occasional excess, in the later stages of growth, of exceptionally long cells. This formula suggests that we are dealing with a condition where the cells elongate, but where division is delayed, and depends upon a favourable conjunction of certain independent events in the cell. (If the probability of division becomes too small, this law itself will break down.) During the growth cycle l̄ passes through a maximum and then decreases, most of the snake-forms disappearing again—though some occasionally persist in excess of expectation: these may be forms of low viability. A size coefficient, σ, is defined which gives a good representation of the abnormality of the appearance of the culture under the microscope, and serves to characterize the distribution of lengths. σ and l̄ decrease as the osmotic pressure of the medium is increased by the addition of salts or of erythrite. With successive passages of a culture through the ammonium sulphate medium the power to give the snake-forms shows a regular decline and is finally lost. It does not appear to be easily restored by several passages through bouillon. The tendency to give snake-forms is enhanced by one preliminary passage through a medium containing asparagine, but growth in an asparagine medium gives normal forms. Experiments on the effect of centrifuged medium from old cultures, of inoculum size and age, and of glucose concentration on σ and on the lag, taken in conjunction with previous work on the lag phase of Bact. lactis aerogenes , lead to the following hypothesis: Two separate factors L and D , one of which, L , is diffusible into the medium, the other, D , being probably retained by the cells, are responsible respectively for elongation and for division. D may be consumed or diluted in the process of division: and its formation may be accelerated or impeded by the presence of other substances in the medium. If the cells are transferred to a new medium, the rates of formation of L and D may be out of balance and snake-forms appear. Successive passages restore the balance by a process of ‘training’. The mechanism of the training is discussed in the light of a hypothesis in which a crude model of enzyme synthesis having certain analogies with crystal growth is used.

The effect of inorganic and organic mercury on growth kinetics of Nitzschia acicularis W. Sm. and Tetraselmis suecica Butch.

1980 ◽  
Vol 26 (8) ◽  
pp. 930-937 ◽  
Author(s):  
B. Mora ◽  
J. Fábregas
Keyword(s):  
Growth Kinetics ◽  
Mercuric Acetate ◽  
Gradual Increase ◽  
Inorganic Mercury ◽  
Inoculum Size ◽  
Lag Phase ◽  
Tetraselmis Suecica ◽  
Initial Effect ◽  
Cellular Area ◽  
Kinetics Of

Studies have been made on the toxicities of three inorganic (HgCl2, HgSO4, and NH2HgCl) and two organic (CH3HgCl and phenyl mercuric acetate (PMA)) mercury derivatives on planktonic algae (Nitzschia acicularis W. Sm. and Tetraselmis suecica Butch.). Growth kinetics and fluorescence changes were used as criteria for assessing algal–metal responses.Methylmercury chloride was found to be the more toxic form, inhibiting growth of both species at levels of 0.025 ppm Hg. PMA inhibited Nitzschia at the same concentration. Inorganic forms prevent growth of the diatom at 0.15–0.20 ppm Hg. Addition of inorganic mercury at concentrations of 0.05 ppm Hg resulted in reduction of the lag phase, increase in exponential growth rate, or both. Increasing mercury concentrations caused a gradual increase in the lag phase in T. suecica and in N. acicularis only with mercuric sulphate. Populations recovered from this initial effect and started to grow. The effect of inoculum size on mercurial toxicity was tested. The higher concentrations of mercury that still permit growth restricted the chlorophyll fluorescence to the central cellular area and the cells appear slimmed. This effect is highest in concentrations that inhibit growth.

scholarly journals The SNARC Effect in the Processing of Second-Language Number Words: Further Evidence for Strong Lexico-Semantic Connections

2008 ◽  
Vol 61 (3) ◽  
pp. 444-458 ◽  
Author(s):  
Jolien De Brauwer ◽  
Wouter Duyck ◽  
Marc Brysbaert
Keyword(s):  
Second Language ◽  
Number Line ◽  
Snarc Effect ◽  
Left Hand ◽  
Number Words ◽  
Number Magnitude ◽  
Large Numbers ◽  
Word Translation ◽  
New Evidence ◽  
Semantic Mediation

We present new evidence that word translation involves semantic mediation. It has been shown that participants react faster to small numbers with their left hand and to large numbers with their right hand. This SNARC (spatial-numerical association of response codes) effect is due to the fact that in Western cultures the semantic number line is oriented from left (small) to right (large). We obtained a SNARC effect when participants had to indicate the parity of second-language (L2) number words, but not when they had to indicate whether L2 number words contained a particular sound. Crucially, the SNARC effect was also obtained in a translation verification task, indicating that this task involved the activation of number magnitude.

scholarly journals Biodegradation of chlorpyrifos using isolates  from contaminated agricultural soil, its kinetic studies

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Muhammad Farhan ◽  
Maqsood Ahmad ◽  
Amina Kanwal ◽  
Zahid Ali Butt ◽  
Qaiser Farid Khan ◽  
...  
Keyword(s):  
Bacillus Cereus ◽  
Contaminated Soils ◽  
Farmyard Manure ◽  
Kinetic Studies ◽  
Inoculum Size ◽  
Lag Phase ◽  
Design Matrix ◽  
Burman Design ◽  
Experimental Values ◽  
Plackett Burman Design

AbstractExtensive pesticides use is negatively disturbing the environment and humans. Pesticide bioremediation with eco-friendly techniques bears prime importance. This study evaluates the bioremediation of chlorpyrifos in soil using indigenous Bacillus cereus Ct3, isolated from cotton growing soils. Strains were identified through ribotyping (16s rRNA) by Macrogen (Macrogen Inc. Geumchen-gu, South Korea). Bacillus cereus Ct3 was resistant up to 125 mg L−1 of chlorpyrifos and successfully degraded 88% of chlorpyfifos in 8 days at pH 8. Bacillus cereus Ct3 tolerated about 30–40 °C of temperature, this is a good sign for in situ bioremediation. Green compost, farmyard manure and rice husk were tested, where ANOVA (P < 0.05) and Plackett–Burman design, results indicated that the farm yard manure has significant impact on degradation. It reduced the lag phase and brought maximum degradation up to 88%. Inoculum size is a statistically significant (P < 0.05) factor and below 106 (CFU g−1) show lag phase of 4–6 days. Michaelis–Menten model results were as follows; R2 = 0.9919, Vmax = 18.8, Ks = 121.4 and Vmax/Ks = 0.1546. GC–MS study revealed that chlorpyrifos first converted into diethylthiophosphoric acid and 3,5,6-trichloro-2-pyridinol (TCP). Later, TCP ring was broken and it was completely mineralized without any toxic byproduct. Plackett–Burman design was employed to investigate the effect of five factors. The correlation coefficient (R2) between experimental and predicted value is 0.94. Central composite design (CBD) was employed with design matrix of thirty one predicted and experimental values of chlorpyrifos degradation, having “lack of fit P value” of “0.00”. The regression coefficient obtained was R2 = 0.93 which indicate that the experimental vales and the predicted values are closely fitted. The most significant factors highlighted in CBD/ANOVA and surface response plots were chlorpyrifor concentration and inoculum size. Bacillus cereus Ct3 effectively degraded chlorpyrifos and can successfully be used for bioremediation of chlorpyrifos contaminated soils.

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