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1.
Amaya-Delgado L Vega-Estrada J Flores-Cotera LB Dendooven L Hidalgo-Lara ME Montes-Horcasitas MC 《Applied microbiology and biotechnology》2006,70(4):477-481
The effect of cell density on xylanolytic activity and productivity of Cellulomonas flavigena was evaluated under two different culturing conditions: fed-batch culture with discontinuous feed of sugar cane bagasse (SCB;
condition 1) and glycerol fed-batch culture followed by addition of SBC as xylanases inducer (condition 2). The enzymatic
profile of xylanases was similar in both systems, regardless of the initial cell density at time of induction. However, the
xylanolytic activity changed with initial cell density at the time of induction (condition 2). The maximum volumetric xylanase
activity increased with increased initial cell density from 4 to 34 g l−1 but decreased above this value. The largest total volumetric xylanase productivity under condition 2 (1.3 IU ml−1 h−1) was significantly greater compared to condition 1 (maximum 0.6 IU ml−1 h−1). Consequently, induction of xylanase activity by SCB after growing of C. flavigena on glycerol at intermediate cell density can be a feasible alternative to improve activity and productivity of xylanolytic
enzymes. 相似文献
2.
Candida cylindracea NRRL Y-17506 was grown to produce extracellular lipase from oleic acid as a carbon source. Through flask cultures, it was found that the optimum initial oleic acid concentration for cell growth was 20 g l−1. However, high initial concentrations of oleic acid up to 50 g l−1 were not inhibitory. The highest extracellular lipase activity obtained in flask culture was 3.0 U ml−1 after 48 h with 5 g l−1 of initial oleic acid concentration. Fed-batch cultures (intermittent and stepwise feeding) were carried out to improve cell concentration and lipase activity. For the intermittent feeding fed-batch culture, the final cell concentration was 52 g l−1 and the extracellular lipase activity was 6.3 U ml−1 at 138.5 h. Stepwise feeding fed-batch cultures were carried out to simulate an exponential feeding and to investigate the effects of specific growth rate (0.02, 0.04 and 0.08 h−1) on cell growth and lipase production. The highest final cell concentration obtained was 90 g l−1 when the set point of specific growth rate (μset) was 0.02 h−1. High specific growth rate (0.04 and 0.08 h−1) decreased extracellular lipase production in the later part of fed-batch cultures due to build-up of the oleic acid oversupplied. The highest extracellular lipase activity was 23.7 U ml−1 when μset was 0.02 h−1, while the highest lipase productivity was 0.31 U ml−1 h−1 at μset of 0.08 h−1. 相似文献
3.
The freshwater microalga Chlorella vulgaris was grown heterotrophically in fed-batch 50–600-L fermenters at 36°C, on aerated and mixed nutrient solution with urea as
a nitrogen and glucose as a carbon and energy source. Cell density increased from the initial value 6.25 to 117.18 g DW L−1 in 32 h in the fermenter 50 L at a mean growth rate 3.52 g DW L−1 h−1. The DW increase in the fermenter 200 L was from 7.25 to 94.82 g DW L−1 in 26.5 h at a mean growth rate 3.37 g DW L−1 h−1. Mean specific growth rate μ was about 0.1 h−1 in the both fermenters, if nutrients and oxygen were adequately supplied. The DW increase in the fermenter 600 L was from
0.8 to 81.6 g DW L−1 in 66.5 h at a mean growth rate 1.22 g DW L−1 h−1 and μ = 0.07 h−1. A limitation of the cell growth rate in 600 L fermenter caused by a low dissolved oxygen concentration above cell densities
higher than 10 g DW L−1) occurred. Specific growth rate decreased approximately linearly with increasing glucose concentration (25–80 g glucose L−1) at the beginning of cultivation and decreased with the time of cultivation. The cell yield was 0.55–0.69 g DW (g glucose)−1. The content of proteins, β-carotene, and chlorophylls in the cells steadily increased and starch content decreased, by keeping
aerated and mixed culture another 12 h in fermenter after the cell growth was stopped due to glucose deficiency. 相似文献
4.
Christopher J. Hewitt Ken Lee Alvin W. Nienow Robert J. Thomas Mark Smith Colin R. Thomas 《Biotechnology letters》2011,33(11):2325-2335
The effects on human mesenchymal stem cell growth of choosing either of two spinner flask impeller geometries, two microcarrier
concentrations and two cell concentrations (seeding densities) were investigated. Cytodex 3 microcarriers were not damaged
when held at the minimum speed, NJS, for their suspension, using either impeller, nor was there any observable damage to the cells. The maximum cell density
was achieved after 8–10 days of culture with up to a 20-fold expansion in terms of cells per microcarrier. An increase in
microcarrier concentration or seeding density generally had a deleterious or neutral effect, as previously observed for human
fibroblast cultures. The choice of impeller was significant, as was incorporation of a 1 day delay before agitation to allow
initial attachment of cells. The best conditions for cell expansion on the microcarriers in the flasks were 3,000 microcarriers
ml−1 (ca. 1 g dry weight l−1), a seeding density of 5 cells per microcarrier with a 1 day delay before agitation began at NJS (30 rpm), using a horizontally suspended flea impeller with an added vertical paddle. These findings were interpreted using
Kolmogorov’s theory of isotropic turbulence. 相似文献
5.
Viral abundance, burst sizes, lytic production and temperate phage were investigated in land-fast ice at two sites in Prydz
Bay Antarctica (68°S, 77°E) between April and November 2008. Both ice cores and brine were collected. There was no seasonal
pattern in viral or bacterial numbers. Across the two sites virus abundances ranged between 0.5 × 105 and 5.1 × 105 viruses ml−1 in melted ice cores and 0.6 × 105–3.5 × 105 viruses ml−1 in brine, and bacterial abundances between 2.7 × 104 and 17.3 × 104 cells ml−1 in melted ice cores and 3.9 × 104–32.5 × 104 cells ml−1 in brine. Virus to bacterium ratios (VBR) showed a clear seasonal pattern in ice cores with lowest values in winter (range
1.2–20.8), while VBRs in brine were lower (0.2–4.9). Lytic viral production range from undetectable to 2.0 × 104 viruses ml−1 h−1 in ice cores with maximum rates in September and November. In brine maximum, lytic viral production occurred in November
(1.18 × 104 viruses ml−1 h−1). Low burst sizes were typical (3.94–4.03 viruses per bacterium in ice cores and 3.16–4.0 viruses per bacterium in brine)
with unusually high levels of visibly infected cells—range 40–50%. This long-term investigation revealed that viral activity
was apparent within the sea ice throughout its annual cycle. The findings are discussed within the context of limited data
available on viruses in sea ice. 相似文献
6.
The continuous fermentation of 1,3-propanediol from glycerol by Clostridium butyricum was subjected to cell recycling by filtration using hollow-fibre modules made from polysulphone. The performance of the culture
system was checked at a retention ratio (dilution rate/bleed rate) of 5, dilution rates between 0.2 h−1 and 1.0 h−1 and glycerol input concentrations of 32 g l−1 and 56 g l−1. The near-to-optimum propanediol concentration of 26.5 g l−1 (for 56 g l−1 glycerol) was maintained up to a dilution rate of 0.5 h−1 and then decreased while the propanediol productivity was highest at 0.7 h−1. The productivity could be increased by a factor of four in comparison to the continuous culture without cell recycling.
By application of the model of Zeng and Deckwer [(1995) Biotechnol Prog 11: 71–79] for cultures under substrate excess, it
was shown that the limitations resulted exclusively from product inhibition and detrimental influences from the cell recycling
system, such as shear stress, were not involved.
Received: 20 October 1997 / Received revision: 12 December 1997 / Accepted: 14 December 1997 相似文献
7.
Lakkana Laopaiboon Pornthap Thanonkeo Prasit Jaisil Pattana Laopaiboon 《World journal of microbiology & biotechnology》2007,23(10):1497-1501
Sweet sorghum juice supplemented with 0.5% ammonium sulphate was used as a substrate for ethanol production by Saccharomyces cerevisiae TISTR 5048. In batch fermentation, kinetic parameters for ethanol production depended on initial cell and sugar concentrations.
The optimum initial cell and sugar concentrations in the batch fermentation were 1 × 108 cells ml−1 and 24 °Bx respectively. At these conditions, ethanol concentration produced (P), yield (Y
ps) and productivity (Q
p
) were 100 g l−1, 0.42 g g−1 and 1.67 g l−1 h−1 respectively. In fed-batch fermentation, the optimum substrate feeding strategy for ethanol production at the initial sugar
concentration of 24 °Bx was one-time substrate feeding, where P, Y
ps and Q
p
were 120 g l−1, 0.48 g g−1 and 1.11 g l−1 h−1 respectively. These findings suggest that fed-batch fermentation improves the efficiency of ethanol production in terms of
ethanol concentration and product yield. 相似文献
8.
Alginate concentrations between 2 and 4% had little effect on the degradation rate of phenol by alginate-immobilized Pseudomonas putida. Ten-degree shifts from 25°C resulted in approximately 30% slower degradation. Maximal degradation rates were favored at
pH 5.5–6.0. The response of degradation rate to increased air flow in the bubble column used was almost linear and an optimal
higher than 16 vol vol−1 was indicated, although free cells appeared in the reaction medium above 12 vol vol−1. When the initial phenol concentration was raised, degradation rate was not significantly affected until levels higher than
1200 mg ml−1 where performance was markedly reduced. Increasing the ratio of total bead volume to medium volume gave progressively smaller
increases in degradation rate. At a medium volume to total bead volume ratio of 5:1, the maximum degradation rate was 250
mg L−1 h−1.
Received 24 November 1998/ Accepted in revised form 27 January 1999 相似文献
9.
The growth performance of malolactic fermenting bacteria Oenococcus oeni NCIMB 11648 and Lactobacillus brevis X2 was assessed in continuous culture. O. oeni grew at a dilution rate range of 0.007 to 0.052 h−1 in a mixture of 5:6 (g l−1) of glucose/fructose at an optimal pH of 4.5, and L. brevis X2 grew at 0.010 to 0.089 h−1 in 10 g l−1 glucose at an optimal pH of 5.5 in a simple and safe medium. The cell dry weight, substrate uptake and product formation
were monitored, as well as growth kinetics, yield parameters and fermentation balances were also evaluated under pH control
conditions. A comparison of growth characteristics of two strains was made, and this showed significantly different performance.
O. oeni has lower maximum specific growth rate (μmax=0.073 h−1), lower maximum cell productivity (Q
x
max=17.6 mg cell l−1 h−1), lower maximum biomass yield (Y
x/s
max=7.93 g cell mol−1 sugar) and higher maintenance coefficient (m
s=0.45 mmol−1 sugar g−1 cell h−1) as compared with L. brevis X2 (μmax=0.110 h−1; Q
x
max=93.2 g−1 cell mol−1 glucose; Y
x/s
max=22.3 g cell mol−1 glucose; m
s=0.21 mmol−1 glucose g−1 cell h−1). These data suggest a possible more productive strategy for their combined use in maturation of cider and wine. 相似文献
10.
Mineralization of pentachlorophenol in a contaminated soil by Pseudomonas sp UG30 cells encapsulated in κ-carrageenan 总被引:2,自引:0,他引:2
M B Cassidy H Mullineers H Lee J T Trevors 《Journal of industrial microbiology & biotechnology》1997,18(1):43-48
A fermentation process in Escherichia coli for production of supercoiled plasmid DNA for use as a DNA vaccine was developed using an automated feed-back control nutrient
feeding strategy based on dissolved oxygen (DO) and pH. The process was further automated through a computer-aided data
processing system to regulate the cell growth rate by controlling interactively both the nutrient feed rate and agitation
speed based on DO. The process increased the total yield of the plasmid DNA by approximately 10-fold as compared to a manual
fed-batch culture. The final cell yield from the automated process reached 60 g L−1 of dry cell weight (OD600 = 120) within 24 h. A plasmid DNA yield of 100 mg L−1 (1.7 mg g−1 cell weight) was achieved by using an alkaline cell lysis method. Plasmid yield was confirmed using High Performance Liquid
Chromatography (HPLC) analysis. Because cells had been grown under carbon-limiting conditions in the automated process,
acetic acid production was minimal (below 0.01 g L−1) throughout the fed-batch stage. In contrast, in the manual process, an acid accumulation rate as high as 0.36 g L−1 was observed, presumably due to the high nutrient feed rates used to maintain a maximum growth rate. The manual fed-batch
process produced a low cell density averaging 10–12 g L−1 (OD600 = 25–30) and plasmid yields of 5–8 mg L−1 (approximately 0.7 mg g−1 cells). The improved plasmid DNA yields in the DO- and pH-based feed-back controlled process were assumed to be a result
of a combination of increased cell density, reduced growth rate (μ) from 0.69 h−1 to 0.13 h−1 and the carbon/nitrogen limitation in the fed-batch stage. The DO- and pH-based feed-back control, fed-batch process has
proven itself to be advantageous in regulating cell growth rate to achieve both high cell density and plasmid yield without
having to use pure oxygen. The process was reproducible in triplicate fermentations at both 7-L and 80-L scales.
Received 22 March 1996/ Accepted in revised form 20 September 1996 相似文献
11.
TiO2 nanofibers with uniform diameter about 125 nm were prepared based on sol–gel process and electrospinning technology. Protex
6L, an industrial alkaline protease, was covalently immobilized on TiO2 nanofiber through γ-aminopropyltriethoxysilane modification and glutaraldehyde crosslinking. With 2 (v/v)% glutaraldehyde
as crosslinker, the enzyme loading is about 201 mg (g nanofiber membrane)−1, and the specific activity of the immobilized Protex 6L is 2.45 μmol h−1 ml−1 mg−1 protein for synthesis of sucrose monolaurate from sucrose and vinyl laurate. The optimal condition for sucrose monolaurate
production is 5% (v/v) water content in DMSO/2-methyl-2-butanol solvent mixture and 50°C. Under this condition, 97% conversion
was achieved within 36 h by nanofibrous Protex 6L, which is corresponding to a productivity 34 times higher than that of most
widely used Novozym 435. After 10 cycles reuse, nanofibrous Protex 6L retained 52.4% of its original activity. 相似文献
12.
A method for plant regeneration in Robinia pseudoacacia L. from cell suspension culture was established. Non regenerative friable callus from hypocotyls and cotyledon explants from
in vitro raised seedling induced on solid Murashige and Skoog (MS) medium supplemented with 0.05 mg dm−3 2,4-dichlorophenoxyacetic acid (2,4-D) was used for initiation of cell suspension cultures on same MS medium but without
agar. Single cells were isolated after 3 d and the optimum cell density was 1–3 × 104 cells per cm3 of the liquid MS medium. Plating efficiency was 29.6 % and callus formed within 4 weeks was subcultured and transferred to
solid MS medium supplemented with 0.6 mg dm−3 benzyladenine (BA) along with 0.05 mg dm−3 α-naphthalene-1-acetic acid (NAA) for the induction of adventitious bud primordia. The shoots developed were isolated and
re-cultured on MS medium containing 0.6 mg dm−3 BA. These microshoots after dipping in 1–2 cm3 of 10 mg dm−3 indole-3-butyric acid (IBA) for 24 h in dark were cultured on half strength solid MS medium supplemented with 0.05 % charcoal
and showed 80–82 % rooting within 4 weeks. 相似文献
13.
To search for an alternative method for protoplast culture, regenerable embryogenic calli were obtained from anther culture
of three wheat cultivars, Karl 92, Jinghua #1, and Pavon 76. Protoplasts were isolated directly from the haploid embryogenic
calli and cultured in modified PMI and LM8P media without going through cell suspension culture. After 8–11 days of subculture,
the embryogenic calli produced the maximum yield of protoplasts and cell division was at the highest frequency when plated
at a density of 3–4 × 105 protoplasts ml−1. Frequency of colony formation varied from 0.2% to 0.5% for Jinghua #1 and from 0.1% to 2% for Pavon 76, while Karl 92 failed
to produce colonies, even though its embryogenic calli were friable and fast-growing on the maintenance medium. Green haploid
plantlets of Jinghua #1 and Pavon 76 have been regenerated from protoplasts, which were cultured on a differentiation medium
first and then on a rooting medium.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
Boiero L Perrig D Masciarelli O Penna C Cassán F Luna V 《Applied microbiology and biotechnology》2007,74(4):874-880
The aim of this work was to evaluate phytohormone biosynthesis, siderophores production, and phosphate solubilization in three
strains (E109, USDA110, and SEMIA5080) of Bradyrhizobium japonicum, most commonly used for inoculation of soybean and nonlegumes in USA, Canada, and South America. Siderophore production and
phosphate solubilization were evaluated in selective culture conditions, which had negative results. Indole-3-acetic acid
(IAA), gibberellic acid (GA3), and abscisic acid (ABA) production were analyzed by gas chromatography–mass spectrometry (GC-MS). Ethylene and zeatin biosynthesis
were determined by GS–flame ionization detection and high-performance liquid chromatography (HPLC-UV), respectively. IAA,
zeatin, and GA3 were found in all three strains; however, their levels were significantly higher (p < 0.01) in SEMIA5080 (3.8 μg ml−1), USDA110 (2.5 μg ml−1), and E109 (0.87 μg ml−1), respectively. ABA biosynthesis was detected only in USDA110 (0.019 μg ml−1). Ethylene was found in all three strains, with highest production rate (18.1 ng ml−1 h−1) in E109 cultured in yeast extract mannitol medium plus l-methionine. This is the first report of IAA, GA3, zeatin, ethylene, and ABA production by B. japonicum in pure cultures, using quantitative physicochemical methodology. The three strains have differential capability to produce
the five major phytohormones and this fact may have an important technological implication for inoculant formulation. 相似文献
15.
High-cell-density production of recombinant growth hormone of Lateolabrax japonicus (rljGH) expressed intracellularly in Pichia pastoris was investigated. In the regular strategy of induction at a cell density of 160 g l−1, short duration of intracellular rljGH accumulation (17 h) resulted in a low final cell density of 226 g l−1. Thus, a novel strategy of induction at a cell density of 320 g l−1 was investigated. In this strategy, the preinduction glycerol-feeding scheme had a significant effect on the post-induction
production. Constant glycerol feeding led to a decrease of the specific rljGH production and specific production rate because
of low preinduction specific growth rate. This decrease was avoided by exponential glycerol feeding to maintain a preinduction
specific growth rate of 0.16 h−1. The results from exponential glycerol feeding indicated that the rljGH production depended on the preinduction specific
growth rate. Moreover, mixed feeding of methanol and glycerol during induction improved the specific production rate to 0.07 mg
g−1 h−1 from 0.043 mg g−1 h−1. Consequently, both high cell density (428 g l−1) and high rljGH production could be achieved by the novel strategy: growing the cells at the specific growth rate of 0.16 h−1 to the cell density of 320 g l−1 and inducing the expression by mixed feeding. 相似文献
16.
Summary Use of lysozyme was tested for treatment of bacterial contaminations in in vitro shoot cultures of quince (Cydonia oblonga) ‘BA 29’ and the hybrid (Prunus persica × P. amygdalus) rootstock ‘GF 677’. Shoots which had been contaminated for about 1 yr by Bacillus circulans and Sphingomonas paucimobilis were treated in liquid culture, at pH 4.5, with 9–36 mg ml−1 egg white lysozyme (EWL), and compared to each other and to untreated cultures for their growth, proliferation, and number
of bacterial colony-forming units in the tissues. EWL did not negatively affect shoot growth up to 18 mg ml−1; furthermore, the proliferation rates of EWL-treated shoots were sometimes higher than those of controls. In contrast, the
concentration of 36 mg ml−1 had some deleterious effect on the regrowth capacity and shoot production of ‘GF 677’ at the first subculture to solid medium
after EWL, treatments. EWL had a simple bacteriostatic effect against Sphingomonas paucimobilis; in contrast, it was effective at 18 mg ml−1 in eliminating Bacillus circulans in both ‘BA 29’ and ‘GF 677’ cultures, after optimal treatment duration. 相似文献
17.
Mukunda Goswami Wazir S. Lakra T. Rajaswaminathan Gourav Rathore 《Molecular biology reports》2010,37(4):2043-2048
A new cell culture system (MRH) was developed for the first time from 2 months old freshwater prawn, Macrobrachium rosenbergii. Primary cultures were developed from heart tissues by explant culture technique. Cell outgrowth was obtained from the heart
explant after 14 days of explant culture. The culture medium used was Leibovitz-15 supplemented with 20% Fetal Bovine Serum
along with 1% prawn hemolymph serum, 0.1% glucose, 0.5% NaCl and antibiotics (Penicillin 10,000 Units ml−1, Streptomycin 10,000 μg ml−1, Amphotericin B 500 mg ml−1) with a final osmomolality of 470–550 mmol kg−1. The pH of the growth medium found suitable for the growth of the cells was 7.20. The viability of cells was found to be
60% when revived after a month of storage in liquid nitrogen. 相似文献
18.
Teresa Manso Carla Nunes Sara Raposo Maria Emília Lima-Costa 《Journal of industrial microbiology & biotechnology》2010,37(11):1145-1155
Large-scale production has been the major obstacle to the success of many biopesticides. The spreading of microbial biocontrol
agents against postharvest disease, as a safe and environmentally friendly alternative to synthetic fungicides, is quite dependent
on their industrial mass production from low-cost raw materials. Considerable interest has been shown in using agricultural
waste products and by-products from food industry as nitrogen and carbon sources. In this work, carob pulp aqueous extracts
were used as carbon source in the production of the biocontrol agent Pantoea agglomerans PBC-1. Optimal sugar extraction was achieved at a solid/liquid ratio of 1:10 (w/v), at 25°C, for 1 h. Batch experiments were
performed in shake flasks, at different concentrations and in stirred reactors at two initial inoculums concentrations, 106 and 107 cfu ml−1. The initial sugar concentration of 5 g l−1 allowed rapid growth (0.16 h−1) and high biomass productivity (0.28 g l−1 h−1) and was chosen as the value for use in stirred reactor experiments. After 22 and 32 h of fermentation the viable population
reached was 3.2 × 109 and 6.2 × 109 cfu ml−1 in the fermenter inoculated at 106 cfu ml−1 and 2.7 × 109 and 6.7 × 109 cfu ml−1 in the bioreactor inoculated at 107 cfu ml−1. A 78% reduction of the pathogen incidence was achieved with PBC-1 at 1 × 108 cfu ml−1, grown in medium with carob extracts, on artificially wounded apples stored after 7 days at 25°C against P. expansum. 相似文献
19.
A Pseudomonas sp. strain NGK 1 (NCIM 5120) was immobilized in various matrices, namely, alginate, agar (1.8 × 1011 cfu g−1 beads) and polyacrylamide (1.6 × 1011 cfu g−1 beads). The degradation of naphthalene was studied, by freely suspended cells (4 × 1010 cfu ml−1) and immobilized cells in batches, with shaken culture and continuous degradation in a packed-bed reactor. Free cells brought
about the complete degradation of 25 mmol naphthalene after 3 days of incubation, whereas, a maximum of 30 mmol naphthalene
was degraded by the bacteria after 3–4 days of incubation with 50 mmol and 75 mmol naphthalene, and no further degradation
was observed even after 15 days of incubation. Alginate-entrapped cells had degraded 25 mmol naphthalene after 3.5 days of
incubation, whereas agar- and polyacrylamide-entrapped cells took 2.5 days; 50 mmol naphthalene was completely degraded by
the immobilized cells after 6–7 days of incubation. Maximum amounts of 55 mmol, 70 mmol and 67 mmol naphthalene were degraded,
from an initial 75 mmol naphthalene, by the alginate-, agar- and polyacrylamide-entrapped cells after 15 days of incubation.
When the cell concentrations were doubled, 25 mmol and 50 mmol naphthalene were degraded after 2 and 5.5 days of incubation
by the immobilized cells. Complete degradation of 75 mmol naphthalene occurred after 10 days incubation with agar- and polyacrylamide-entrapped␣cells,
whereas only 60 mmol naphthalene was degraded by alginate-entrapped cells after 15 days of␣incubation. Further, with 25 mmol
naphthalene, alginate-, agar- and polyacrylamide-entrapped cells (1.8 × 1011 cfu g−1 beads) could be reused 18, 12 and 23 times respectively. During continuous degradation in a packed-bed reactor, 80 mmol naphthalene
100 ml−1 h−1 was degraded by alginate- and polyacrylamide-entrapped cells whereas 80 mmol naphthalene 125 ml−1␣h−1 was degraded by agar-entrapped cells.
Received: 21 October 1997 / Received revision: 15 January 1998 / Accepted: 18 January 1998 相似文献
20.
Antarctic lakes are extreme ecosystems with microbially dominated food webs, in which viruses may be important in controlling
community dynamics. A year long investigation of two Antarctic saline lakes (Ace and Pendant Lakes) revealed high concentrations
of virus like particles (VLP) (0.20–1.26 × 108 ml−1), high VLP: bacteria ratios (maximum 70.6) and a seasonal pattern of lysogeny differing from that seen at lower latitudes.
Highest rates of lysogeny (up to 32% in Pendant Lake and 71% in Ace Lake) occurred in winter and spring, with low or no lysogeny
in summer. Rates of virus production (range 0.176–0.823 × 106 viruses ml−1 h−1) were comparable to lower latitude freshwater lakes. In Ace Lake VLP did not correlate with bacterial cell concentration
or bacterial production but correlated positively with primary production, while in Pendant Lake VLP abundance correlated
positively with both bacterial cell numbers and bacterial production but not with primary production. In terms of virus and
bacterial dynamics the two saline Antarctic lakes studied appear distinct from other aquatic ecosystems investigated so far,
in having very high viral to bacterial ratios (VBR) and a very high occurrence of lysogeny in winter. 相似文献