KARKATA FARANTIN KUMA ƘWAYOYIN CUTA SU BAZU ZUWA ƘASA

Tururuwa (swarming) hanya ce da wasu ƙwayoyin cuta ke tafiya tare: cunkoson ƙwayoyi masu motsi suna bazuwa a kan fuska mai laushi da danshi, a cikin siraren ruwa, suna samar da tarurruka, juye-juye da kwararar gama-gari. A dakin gwaji, taruruwa suna girma zuwa da’ira, siffofi masu rassa ko zare-zare.

Yanayin zahiri na kewayensu yana da muhimmanci — yawan ruwan da gel ke bayarwa, jan saman (surface tension) siraren ruwan. Amma wani abu ɗaya an yi watsi da shi sosai, in ji takardar: nauyi (gravity). Gwaje-gwaje na yau da kullum suna amfani da faranti a kwance, inda nauyi ke zama tsayayyen yanayi maras tasiri. Wani tsohon bincike, da marubutan suka ambata, ya nuna cewa alkiblar nauyi ta canza siffar rukunonin staphylococci da aka shuka a gel mai laushi.

Kusurwoyi takwas, daga kwance zuwa juye

Pengxi Gu, Zijie Qu da abokan aikinsu a Kwalejin Duniya ta Jami’ar Shanghai Jiao Tong, tare da abokan rubutu a Cibiyar Fasaha ta Georgia, Jami’ar Johns Hopkins da Jami’ar Fudan, sun yi aiki da Enterobacter sp. SM3, ƙwayar cuta mai tururuwa da aka fara ware ta daga hanjin ɓera — muhallin da fuskokinsa ke lanƙwasa kuma ba safai suke a kwance ba. A kan faranti a kwance, SM3 yana samar da rukuni kusan zagaye, abin kwatance mai tsabta.

Sun sanya ɗigon ƙwayoyin cuta a tsakiyar faranti na gel mai laushi, sun bar taron ya fara tsawon sa’o’i uku a kan fuska a kwance, sannan suka sanya farantan a alkibloli takwas: a kwance (0°), a karkace fuskantar sama a 30°, 45° da 75°, a karkace fuskantar ƙasa a 105°, 135° da 150°, da a kwance a juye (180°). Sun ɗauki hoton rukunonin kowace sa’a har zuwa sa’o’i tara — rukunoni 15 masu zaman kansu ga kowace kusurwa — kuma sun ɗauki bidiyon ƙwayoyin da ke motsi a wurare biyar a gefen kowane rukuni ƙarƙashin na’urar hangen ƙananan abubuwa (microscope).

Kusurwoyin tsakiya suka yi nasara

Bambance-bambancen sun taru a hankali. A ƙarshe, girman taron ya dogara da karkatar ta hanyar da ba ta tafiya a layi ɗaya ba (non-monotonic): rukunoni sun fi girma a karkatar tsakiya, mafi girma a 75° da 45°, kuma mafi ƙanƙanta a faranti da ke kusan ko gaba ɗaya a juye (150° da 180°). Faranti da aka ɗan karkata kaɗan kawai, a 30°, sun ɗan yi ƙasa da na kwance a girma.

Gefen da ke fuskantar sama ma yana da muhimmanci. Ma’auratan faranti masu karkata ɗaya, ɗaya yana fuskantar sama ɗaya kuma ƙasa — 30° da 150°, 45° da 135°, 75° da 105° — sun ba da sakamako daban-daban: tsarin fuskantar sama ya fi samar da rukunoni manya a kowace ma’aurata.

Siffofin da aka ja zuwa ƙasan gangare

Rukunonin kwance sun kasance kusan zagaye. Waɗanda aka karkata sun karkace, sun miƙe zuwa gefen ƙasan gangare:

• Ma’aunin rashin daidaiton siffa ya kasance kusan 0.1 a faranti na kwance kuma ya kai 0.90 a 75°.
• Gefen ƙasan gangare ya miƙe kusan ninki 1.46 zuwa 1.52 na nisan gefen sama tsakanin 75° da 135°.
• Wasu rukunoni sun tsiro wutsiya kamar ta tauraro mai wutsiya: a 75°, ƙarshen ƙasan gangare ya ci gaba kusan ninki 2.2 na saurin gefuna biyu maƙwabtansa.

Ƙarƙashin na’urar hangen ƙananan abubuwa, hoton ya fi sarƙaƙiya. Ƙwayoyin galibi sun yi motsi a hankali a faranti da aka karkata fiye da na kwance, kuma a hankali a ƙarshen ƙasan gangare fiye da saman rukunin. Juye-juyen da ke ƙarshen sun ɗan fi ƙanƙanta kuma sun fi yawa. Don haka gaban da ya fi saurin ci gaba shi ne wanda ƙwayoyin suka fi jinkirin motsi a cikinsa — alama ce, in ji marubutan, cewa saurin ƙwayoyi na gida kaɗai ba zai iya bayyana yadda gefen ke ci gaba ba.

Siraren ruwa, da aka ja ta hanyoyi biyu

Don fassara waɗannan yanayi, ƙungiyar ta faɗaɗa wani samfuri da ake da shi na taruruwa a matsayin siraren fim mai matakai biyu na ƙwayoyi da ruwa, ta ƙara nauyi da aka raba zuwa sassa biyu. Ɓangaren da ke tafiya a gefen fuskar yana tura fim ɗin zuwa ƙasan gangare. Ɓangaren da ke ratsa fuskar yana canza matsi a cikin fim ɗin, kuma tare da shi saurin da ruwa ke tsotsewa daga gel ɗin da ke ƙasa.

Samfurin, wanda ba a daidaita shi da ainihin girma ko lokutan gwaje-gwajen ba, ya sake samar da manyan tsare-tsare, har da mafi kyawun kusurwa, 75°. Kashe ɓangare ɗaya a lokaci guda ya fayyace rawar kowanne: nauyi a gefen fuskar ya samar da miƙewa zuwa ƙasan gangare, yayin da ake buƙatar nauyi da ke ratsa ta don bambance faranti masu fuskantar sama da masu fuskantar ƙasa.

Gefen da ya makale kuma ya kuɓuta?

Binciken ya yi amfani da nau’in ƙwayar cuta ɗaya, a cikin yanayin dakin gwaji da aka sarrafa, kuma samfurin bayani ne mai sauƙi. Marubutan sun ba da shawarar cewa a ƙarshen ƙasan gangare, ruwa da ƙwayoyi za su iya taruwa a bayan gefen da ya makale har sai ya kuɓuta ba zato ba tsammani, akai-akai, abin da kuma zai wargaza manyan juye-juye — amma sun yi wa wannan tsari alama a matsayin hasashe, da za a gwada da ma’auni masu daidaito na gaban da kwararar. Babban saƙonsu ya fi sauƙi: a gwaje-gwajen tururuwa, alkiblar fuskar ba ƙaramin abu maras tasiri ba ne.