1) As bactérias são lisadas pelos fosfatos, cuja atividade lítica varia com o sal de fosfato, os trivalentes sendo mais ativos. 2) A fosfatólise independente da viabilidade da bactéria. 3) A fosfatólise póde interferir nas suspensões com tampões de fosfatos e na preservação de hemoculturas.<br>Bacteria are lysed by phosphates in low concentrations. Differences were observed in the lytic activity according to the salt, the trivalente salt being the more active. The lytic action is not always dependent of the living or dead state of the microorganisms. It seems that this "bacterial phosphatolysis" is of importance for the preservation of microorganisms in culture media or in a simple solution containing phosphates.

This paper presents data obtained in a study of the effect of various exchangeable cations on soil aggregation and microorganisms. Twenty-one treatments involving various combinations and ratios of exchangeable Ca, Mg, Na, K, and H were compounded by appropriate treatment of a Hanford sandy loam and a Yolo sandy loam. The soil samples of varying cation composition were incubated alone and in combination with organic matter sources of high and low carbon-nitrogen ratio for a period of 200 days. Soil aggregation measurements and counts of kind and number of soil microorganism were made at various intervals during the incubation period. In comparison with a calcium system, the following results were noted: (1) A high percentage of Mg has no effect on aggregation. (2) Depending on the soil, a high percentage of exchangeable K may or may not reduce aggregation. (3) Increasing Na reduces aggregation. (4) An excess of free lime reduces aggregation. (5) Kinds and numbers of microorganisms are affected more by organic matter additions than by cation composition of soil. (6) Organic matter additions increase aggregation regardless of cation composition.

In the present paper some observations upon the occurence of Azotobacter chroococcum in Finnish soils are reported. Without enrichment Azotobacter could be cultivated on the agar plates only from 5 soils out of the 72 samples tested. The enrichment procedure markedly increased the number of soils that gave positive results in the test. Azotobacter could not be found in soils with a pH value lower than 5.8. On the basis of the results it is concluded that Azotobacter probably is present in a large amount of our less acid soils, although generally, in very low numbers. The phosphorus status of the soil exerted some influence upon the development of inoculated Azotobacter in soil plaques. In soil tests the phosphorus requirement of Azotobacter appeared to be markedly higher than that of the crop plants, in general. It was supposed that in some cases this fact could be explained not only on the basis of the phosphorus need of the bacteria but on the basis of the high sensitivity of the organism to the effects of soil aluminium and iron prevented by phosphates. The cultivation of Azotobacter indicum from the soils failed, but Clostridium species could be found in all the samples tested. The increase in the nitrogen content of the mannitol solution cultures during incubation was highest when the soil contained Azotobacter chroococcum. But also in several cultures of soils from which no Azotobacter could be found by the agar plate method, a considerable increase in nitrogen was observed. This was connected with the formation of a thick membrane of fungi and bacteria on the surface of the liquid. The possibility of nitrogen fixation by the associations of soil microorganisms is discussed.

An attempt has been made to elucidate the influence of lime and fertilizers upon the mineralization of peat nitrogen under laboratory conditions. The main object was to study differences between the responce of various kinds of peats to these treatments and to the incubation under conditions favourable for the activity of microorganisms. The material consisted of eight peat samples from North Finland. Four of them were fen peats with a virgin productivity of 6—8. The other four originated from untillable bogs with a virgin productivity of 1—3. All the samples were from virgin peat lands and only slightly decomposed. In spite of the different origins of these peat groups no marked differences in their chemical composition and characteristics could be found. This was supposed to be due to their low degree of decomposition. In the first large incubation experiment carried out at 15°—22 °C the accumulation of nitrate-nitrogen during the B—lo8—10 months of incubation was relatively high in all the limed samples, but marked nitrification occurred also in most of the un-limed samples, the Sphagnum fuscum peat being the most prominent exception. On the average, the effect of lime upon the total accumulation of mineral nitrogen was positive only in three of the fen peats and in the Sphagnum fuscum sample. In the second experiment lime seemed to stimulate the ammonification in the Sphagnum peats during the first month of incubation, but later on the accumulation of mineral nitrogen was found to be almost equally intensive in the limed and un-limed samples. No significant effect of potassium, phosphorus and nitrogen fertilizers could be stated in the incubation experiments. The same was true in respect to the effect of copper sulphate, zinc chloride or ammonium molybdate. The influence of ash upon the changes in the mineral nitrogen content of one fen peat was supposed to be due to its neutralizing agencies. The accumulation of mineral nitrogen, particularly of ammonium nitrogen, was highest in the untreated samples. Although some superiority of the fen peats to the Sphagnum peats in respect to the speed of the accumulation of mineral nitrogen could be stated, the differences between these groups after the prolonged incubation were negligible. This can be explained by the different intensity of immobilization and denitrification of nitrogen in these peats under the conditions of the experiments. It also may be taken to mean that no distinct differences existed between the decomposability of the nitrogen compounds of these slightly humified fen peats and Sphagnum peats.

In the present paper some observations upon the occurence of Azotobacter chroococcum in Finnish soils are reported. Without enrichment Azotobacter could be cultivated on the agar plates only from 5 soils out of the 72 samples tested. The enrichment procedure markedly increased the number of soils that gave positive results in the test. Azotobacter could not be found in soils with a pH value lower than 5.8. On the basis of the results it is concluded that Azotobacter probably is present in a large amount of our less acid soils, although generally, in very low numbers. The phosphorus status of the soil exerted some influence upon the development of inoculated Azotobacter in soil plaques. In soil tests the phosphorus requirement of Azotobacter appeared to be markedly higher than that of the crop plants, in general. It was supposed that in some cases this fact could be explained not only on the basis of the phosphorus need of the bacteria but on the basis of the high sensitivity of the organism to the effects of soil aluminium and iron prevented by phosphates. The cultivation of Azotobacter indicum from the soils failed, but Clostridium species could be found in all the samples tested. The increase in the nitrogen content of the mannitol solution cultures during incubation was highest when the soil contained Azotobacter chroococcum. But also in several cultures of soils from which no Azotobacter could be found by the agar plate method, a considerable increase in nitrogen was observed. This was connected with the formation of a thick membrane of fungi and bacteria on the surface of the liquid. The possibility of nitrogen fixation by the associations of soil microorganisms is discussed. | Brennerin (2) ja Svinhufvudin (25) ristiriitaiset tulokset Azotobacter chroococcumin esiintymisestä Suomen maaperässä antoivat aiheen edellä olevaan tutkimukseen. Edellisen mukaan Azotobacter on meillä erittäin harvinainen, jälkimmäinen taas löysi sitä kaikista tutkimistaan happamistakin metsämaanäytteistä. Curien (5) agar-malja menetelmää käyttäen todettiin Azotobacteria viidessä tutkituista 72 maanäytteestä. Rikastaminen rouhittamalla pari viikkoa maata, johon oli sekoitettu kalkkia, mannitolia, fosfaattia ja hiven molybdaattia, lisäsi huomattavasti niiden näytteiden lukumäärää, joista kehittyi Azotobacter-pesäkkeitä. Kaikkien näiden pH oli vähintään 5.8. Tulokset viittaavat siihen, että Azotobacteria. on verraten suuressa osassa lievästi happamia maitamme, vaikkakin tavallisesti hyvin niukasti. Azotobacterin fosforin tarve näytti olevan melkoista suurempi kuin viljelyskasvien. Tämän oletettiin johtuvan joko siitä, että organismi pystyy huonosti käyttämään maan fosforiyhdisteitä, tai siitä, että liukenevienfosfaattien lisääminen on tarpeen sitomaan maassa Azotobacterille haitallisessa muodossa olevaa aluminiumia ja rautaa. Suoritettujen kokeitten yhteydessä ei maanäytteistä onnistuttu viljelemään Azotobacter indicumia, mutta Clostridium-lajeja todettiin kaikissa näytteissä. Kokonaistypen määrän lisääntyminen oli suhteellisesti suurin niissä mannitoli-liuos-viljelmissä, jotka oli siirrostettu Azotobacteria sisältävien näytteiden suspensiolla. Mutta myös useitten muitten maanäytteiden viljelmät sitoivat runsaanlaisesti typpeä. Näiden sekä Brennerin (3) vastaavanlaisten havaintojen perusteella näyttää mahdolliselta, että monissa maissa on Clostridium-lajien lisäksi muita bakteereita, ehkä myös hiivoja ja homeita, jotka sekakasvustona pystyvät sitomaan ilmakehän vapaata typpeä.

An attempt has been made to elucidate the influence of lime and fertilizers upon the mineralization of peat nitrogen under laboratory conditions. The main object was to study differences between the responce of various kinds of peats to these treatments and to the incubation under conditions favourable for the activity of microorganisms. The material consisted of eight peat samples from North Finland. Four of them were fen peats with a virgin productivity of 6—8. The other four originated from untillable bogs with a virgin productivity of 1—3. All the samples were from virgin peat lands and only slightly decomposed. In spite of the different origins of these peat groups no marked differences in their chemical composition and characteristics could be found. This was supposed to be due to their low degree of decomposition. In the first large incubation experiment carried out at 15°—22 °C the accumulation of nitrate-nitrogen during the B—lo8—10 months of incubation was relatively high in all the limed samples, but marked nitrification occurred also in most of the un-limed samples, the Sphagnum fuscum peat being the most prominent exception. On the average, the effect of lime upon the total accumulation of mineral nitrogen was positive only in three of the fen peats and in the Sphagnum fuscum sample. In the second experiment lime seemed to stimulate the ammonification in the Sphagnum peats during the first month of incubation, but later on the accumulation of mineral nitrogen was found to be almost equally intensive in the limed and un-limed samples. No significant effect of potassium, phosphorus and nitrogen fertilizers could be stated in the incubation experiments. The same was true in respect to the effect of copper sulphate, zinc chloride or ammonium molybdate. The influence of ash upon the changes in the mineral nitrogen content of one fen peat was supposed to be due to its neutralizing agencies. The accumulation of mineral nitrogen, particularly of ammonium nitrogen, was highest in the untreated samples. Although some superiority of the fen peats to the Sphagnum peats in respect to the speed of the accumulation of mineral nitrogen could be stated, the differences between these groups after the prolonged incubation were negligible. This can be explained by the different intensity of immobilization and denitrification of nitrogen in these peats under the conditions of the experiments. It also may be taken to mean that no distinct differences existed between the decomposability of the nitrogen compounds of these slightly humified fen peats and Sphagnum peats. | Edellä selostetuissa muhituskokeissa tutkittiin kalkin, kali-, fosfaatti- ja typpilannoitteiden sekä tuhkan, kuparin, sinkin ja molybdeenin vaikutusta turvenäytteiden mineraalitypen kertymiseen. Erityisesti kiinnitettiin huomiota eri turvelajien välisiin eroihin. Aineistona oli kahdeksan pohjois-Suomen tyypillisiltä, luonnontilaisilta soilta otettua turvenäytettä. Näytteet 1—4 olivat viljelyskelpoisilta soilta, Bo 6—8, näytteet 5—8 rahkasoilta, joiden boniteetti oli I—3. Kaikki näytteet olivat soiden pintaosasta ja heikosti maatuneita. Huolimatta erilaisesta viljelysarvostaan nämä turveryhmät osoittautuivat kemiallisilta ominaisuuksiltaan yllättävän samanlaisiksi, ainoana poikkeuksena oli maatumaton Sphagnum fuscum-turve, näyte 5. Tähän lienee syynä lähinnä turpeiden alhainen maatumisaste. Kalkitus näytti yleensä edistävän nitrifikaatiota, joskin melkoista nitraattitypen kertymistä oli havaittavissa myös kalkitsemattomissa näytteissä 8—10 kk muhituksen aikana. Kalkin vaikutus mineraalitypen kokonaismäärään oli sen sijaan useissa tapauksissa negatiivinen. Tuhkan vaikutus näytti kytkeytyvän lähinnä sen neutraloiviin ominaisuuksiin. Hivenaineilla, samoin kuin kali- ja fosfaattilannoitteilla ei voitu todeta olevan selvää vaikutusta turpeen typen muutoksiin. Typpilannoitteet alensivat useissa tapauksissa kertyneen mineraalitypen määrää. Vaikka muhituskokeiden tulokset osoittivat melkoisia eroja eri turvelajien mineraalitypen kertymisessä, selvää rajaa ei ollut havaittavissa eri turveryhmien välillä. Ainoastaan muhituksen alkuvaiheessa näytti typen ammonifioituminen olevan hiukan nopeampaa kalkitsemattomissa ja lannoittamattomissa mutasuoturvenäytteissä kuin vastaavissa rahkaturpeissa. On tietenkin otettava huomioon, että tällaisten kokeitten tulokset osoittavat ainoastaan mineraloitumisen, immobilisoitumisen ja denitrifikaation yhteisvaikutusta turpeen typen muutoksiin. Prosessit ovat siis voineet olla hyvinkin erilaiset eri näytteissä samanlaisesta lopputuloksesta huolimatta. Laboratoriokokeet, joissa jauhettua turvetta on muhitettu mahdollisimman suotuisissa olosuhteissa ja joissa kasvien ravinteiden otto sekä ravinteiden huuhtoutuminen eivät pääse vaikuttamaan, antavat tuloksia, jotka voivat poiketa huomattavasti kentällä saatavista. Näitten kokeitten perusteella näyttää kuitenkin siltä, etteivät heikosti maatuneidenrahkaturpeiden typpiyhdisteet olisi sen vaikeammin hajaantuvia kuin heikosti maatuneiden mutasuoturpeiden typpi. Jos luonnon olosuhteissa on havaittavissa eroja samalla maatumisasteella olevien mutasuoturpeiden ja rahkaturpeiden typen mineraloitumisessa, ne johtunevat muista tekijöistä kuin itse typpiyhdisteiden koostumuksesta.