Physiology and Cultivation of
Algae and Cyanobacteria
1.
Definition
• Algae formal tax. standing, polyphyletic origin, artificial assemblage
of O2 evolving photosynthetic organisms
• Algae vs. Plants
the same storage compounds, similar defence strategies against predators & parasites
Plants
•hi degree of differentiation
•repr. organs surrounded by jacket of
sterile cells
•multicell. embryo remains
developmentally & nutrit. independent
on parents
•meristems on root/shoot apices
•digenetic life cycles with alterations
betw. hapl. gametophyte & dipl.
sporophyte
Algae
•don’t have roots, stems, leaves, not well defined
vasc. tissue
•don’t form embryo
•mono- & digenetic life cycles
•occur in dissimilar forms (micro algae, macro a.
multicellular, colonies, branched,…)
•less complexity of the thalli
•hi diversity 0.2 – 60m
ecology & habitats
reserve & structural
polysaccharides
evolutionary origin
•1 – 10 mil. species
•½ primary production in biosphere
Classification
• under constant revision
(Van Den Hoek et al. 1995)
Occurrence & distribution
Aquatic
• almost everywhere (from freshwater spring to salt lakes)
• tolerance of wide range of pH, temp., turbidity, O2 & CO2 conc.
• planctonic
» unicellular, suspended throughout lighted regions of all water (inc. polar ice)
• benthic
» within sediments
» limited to shallow areas (because of rapid attenuation of light with depth)
» attached to stones – epilithic, on mud/sand – epipelic
» on other algae/plants – epiphytic, on animals – epizoic
• marine benthic – after habitat
– supralitoral – above high-tide level within reach wave spray
– intertidal – exposed to tidal cycles
– sublitoral – from extreme low-water to cca 200m deep
• ocean – 71% of earth surface, more than 5000 spec. of planktonic algae
– phytoplankton
» base of marine food chain
» produce 50% of O2 we inhale - life
» death – blooms – too large populations (decrease water transparency, prod. toxins & poisons)
– kelps
» giant algae – temperate pelagic marine environment, till 60m submerged forests
» also beneath polar ice sheet
» can survive at very low depth
– record of 268m u.s.l. – dark blue red algae (blue-green ligh, 0.0005% of surface intensity)
» have accessory pigments, channel the energy to chl a
• accessory & protective pigments – give algae wide variety of colors <> names
https://doi.org/10.1007/s00338-017-1594-5
Occurrence & distribution
Freshwater phytoplankton & benthic algae
» base of aquatic food chain
» not exhibit size range of marine relatives
Subaerial
» life on land
» tree trunks, animal fur, snow, hot springs, desert rocks
» activity – convert rock > soil
− to minimize soil erosion & increase
water retention & nutrient availability for plants
Symbiosis
• lichens, corals
» to survive in environments that they could not alone
Structure o thallus
Unicells & unicell colonial algae
• solitary cells, unicells with/w-out flagella, motile
(Ochromonas)/non-motile (Nannochloris)
• colony
– aggregates of several single cells held together ±organized
– grow – cell division
– each cell can survive solely
• coenobium
– colony with number of cells & arrangement determined at the
time of origin (e.g. Volvox – motile, Pediastrum – non-motile)
Structure of thallus
Filamentous algae
– result from cell division in plane perpendicular to axis of
filament – cell chain
─simple
└branched – true/false
─uniseriate – 1 layer of cells
└multiseriate – up to multiple layer
Syphonous algae
– siphonous/coenocytic construction of tubular filaments
lacking transverse cell walls
– unicellular but multinucleate (coenocytic)
Structure o thallus
Parenchymatous & pseudoparenchymatous algae
– mostly macroscopic
• parenchymatous
» originated from division of primary filament (all
directions)
» lost filamentous structure
• pseudoparenchymatous
» originated from close aggregation of branched
filaments, forming thallus held together with
mucilages (red algae)
Nutrition
• algae = phototrophs
• most algal divisions – contain colorless heterotrophic spec.
– osmotrophy, phagotrophy
– auxotrophy – cannot synthesize essential components (vitamin B12, fatty acids,..) and
have to import them
• algae can use wide spectrum of nutritional strategies
combining:
– phototrophy
– heterotrophy
– mixotrophy (relative contribution of photo.&hetero. can vary)
» often in extreme environment (limiting light,…)
– after nutritional strategies:
– obligate heterotrophic algae – primarily heterotrophs, but capable phototrophy in
limiting prey concentration (Gymnodium gracilentum - Dinophyta)
– obligate phototrophic algae – primarily phototrophs, but capable
phagotrophy/osmotrophy when light is limiting (Dinobryon divergens -
Heterocontophyta)
– facultative mixotrophic algae – can equally well grow as photo-/heterotrophs
(Fragilidinium subglobosum - Dinophyta)
– obligate mixotrophic algae – primary mode is phototrophy & phago-&/osmotrophy
provides essential substances (e.g.photoauxotrphs, Euglena gracilis - Euglenophyta)
Reproduction
• vegetative by division of single cell or
fragmentation of colony
• asexual by production of motile spores
• sexual by union of gametes
– vegetative & asexual
» allow stability of adapted genotypes from generation to the
next
» fast & economical increase of number of individual
» lack genetic variability
– sexual
» involves - plasmogamy (union of cells)
- karyogamy (union of nuclei) - chromosome/gene
association & meiosis >> genetic recombination
» allow variation, but is more costly
Vegetative & Asexual reproduction
• Binary fission & Cellular bisection
– simplest form
– parent org. divides into two equal parts of the same hereditary info as
parent
– unicellular a. - longitudinal
- transverse
– growth of population - lag > exponential > log > stationary (plateau) phase
– in multicellular a. & colonies - leads to the growth of individual
• Zoospore, Aplanospore & Autospore
– zoospores - flagelate motile spores that may be produced within parental
vegetative cell (Clamydomonas - Chlorophyta)
– aplanospores - aflagelate spores that begin their development within
parent cell wall before being released
- can dvelop into zoospores
– autospores - aflagelate daughter cells released from ruptured cell wall of
parental cell, - replicas of vegetative cells that produce them & lack the
capacity to develop into zoospore (Nannochloropsis - Heterocontophyta,
Chlorella - Chlorophyta)
spores - may be produced within - ordinary cells
- specialized sporangia
Vegetative & Asexual reproduction
• Autocolony formation
– coenobium/colony - each cell can produce new colony similar to
parent.
– cell division produce multicellular group (not the unicellular
individuals) > differs from the parent in cell size not in number
e.g. Volvox (Chlorophyta)
– gonidia - series of cells which produce
a hollow sphere within the hollow
of parental colony (released after its rupture)
• Fragmentation
– ± random process whereby non-coenobic colonies/filaments break
into two/several fragments having capacity to develop into new
individual
Vegetative & Asexual reproduction
• Resting stages
– under unfavourable conditions (desiccation)
– thick-walled cells
• hypnospores & hypnozygotes
– thick-walled, produced ex novo from cells previosly separated from parent cells
» hypnospores - Ulothrix spp., Chlorococcum (Chlorophyceae)
» hypnozygotes - Spyrogyra spp. (Chlorophyceae), Dinophyta
– enables algae to survive temporary drying out of small water bodies & allow transport to
another (e.g. via birds)
• statospores
– endogenous cysts formed within vegetative cells by members of Chrysophyceae e.g.
Ochromonas spp.
» cyst walls consist of silica >> preserved as fossils
– spherical, ellipsoidal, often ornamented with spines or other projections
– wall - with pores sealed by unsilicified bung
– within cysts lie nucleus, chloroplasts, reserve material
– after dormancy - germination - form one/several flagellate cells
• akinetes occurrence in blue-green algae
– enlarged vegetative cells that develop thickened wall in response to limiting env. nutrients or
light (e.g. Anabaena cylindrica - Cyanophyta)
– extremely resistant to drying & freezing
– long-term anaerobic storage of genetic material, remain viable in sediments for many years in
hard conditions
– in suitable conditions > germination into new vegetative cells
Sexual reproduction
Gametes
– morphologically identical/different with/from vegetative cells (a. group speciphic
sign)
– haploid DNA content
– possible different gamete types
• isogamy - both gametes types motile & indistinguishable
• heterogamy - gametes differ in size
» anisogamy - both gametes are motile, 1. small - sperm
2. large - egg
» oogamy - 1. motile, small - sperm
2. non-motile, very large - egg
Algae exhibit 3 different life cycles with variation within different groups
• main difference - where meiosis occur & type of cells it produces & whether
there is more than one free-living stages
Sexual reproduction
Haplontic or zygotic life cycle
– single predominant haploid vegetative phase, with meiosis after
germination of zygote
» Chlamydomonas (Chlorophyta)
Diplontic or gametic life cycle
– single predominant diploid vegetative phase
– meiosis gives rise to haploid gametes
» Fucus (Heterocontophyta), Diatoms
Haplontic or zygotic life cycle
Diplontic or gametic life cycle
Sexual reproduction
Diplohaplontic or sporic life cycle
– present alternations of generation between two different phases
consisting of haploide gametophyte & diploid sporophyte
• gametophyte - produce gamete by mitosis
• sporophyte - produce spore by meiosis
– alternation of generations can be
• isomorphic - both phases morphologicaly identical
» Ulva (Chlorophyta)
• heteromorphic - with predominance of
– sporophyte - Laminaria (Heterocontophyta)
– gametophyte - Porhyra (Rodophyta)
Diplohaplontic or sporic life cycle
-isomorphic alternation of generations
Diplohaplontic or sporic life cycle
-heteromorphic alternation of generations